Just to clear up some things about tomenet:
The reason few people play tomenet is that it just isn't a good game. There are a lot of reasons for that, but they basically fall under two categories: Gameplay and developer culture.
The gameplay issues mostly stem from the fact that it's a real time angband variant (think ToME/zangband circa 2002 or so) in which not nearly enough effort has been addressed to the problem of making what is designed to be a turn-based game reasonable for real time play across an internet connection. In angband, almost all actions have instantaneous effects. Crucially, if you read a teleport scroll you are somewhere else the next turn and a monster summons you are surrounded by monsters on the the next turn. This is fine in angband because if you need to, you can really sit and think through your options, which usually include teleporting. In angband, it's maybe not the best game mechanic ever conceived -- a summon can easily put you in a position where you can't survive the next round of combat -- but it's not ridiculous. In tomenet, the next round of combat comes and is over in a fraction of a second. This means your level 48 shaman with greater titan form and over 1500 hp (a character it would take probably 40 hours for a competent player to build) will die essentially instantly in what are in fact fairly common circumstances. If you are summoned on at high levels in an even slightly open area (e.g. in a natural hallway), usually, you MUST teleport within about a quarter of a second or you will die. If you don't live in Paris, adjust that figure for ping.
It takes a lot of unreasonable character deaths for an average player to get that one of the main things (if not the main thing) in tomenet is to avoid getting summoned on. This means not playing open levels, digging or walking through walls whenever possible, and generally playing a very, very tight game where you are never exposed a summoner with more than a couple of open spaces for him to summon on. In general, if you know what you're doing, your higher level characters will only die in two situations: a large, unexpected summon or being breathed on by a pack of high level hounds after coming up or down stairs. (There are some other things that happen, for example you find out you missed a resistance after regearing and get hit for 1500 breath damage or something -- mostly user error type stuff.)
The problem is, this doesn't make for very compelling gameplay. You usually don't even move when you fight at high levels. You just spam spell and potion macros. You take some time to set up, dig tunnels and so forth to avoid summoning, you attack, if things go wrong you teleport. The going wrong part transpires within the space of a second so it's not like there's a lot of complex decision making: Are there suddenly a bunch of Us, Ds, As, Ws, uniques, or flashing Zs? Then teleport immediately. No? Okay, maybe stay a second and reevaluate. If you had to teleport, get off level quickly. When you die, it's often difficult to escape the feeling that you were cheated. There was lag, it happened too fast in comparison to the 40 hours you put into building the character (again, this would happen within a fraction of a second or it wouldn't happen at all), whatever.
At low levels, which are all a typical player ever sees, the issues aren't as obvious. This is where the misconception that the game is good comes from. When you don't know what you're doing, the game looks good. It has what looks like a fairly complex and interesting skill system that would be fun to experiment with. In fact, though, after something like 10 to 15 years of play from people who know everything about the game, there are surprisingly few endgame viable builds and a new player never guesses what they are ("axes or swords? why not both!?" or "ranger seems good. this tox spell really kills orcs!"). So most characters have little chance of surviving past level 35 simply by virtue of poor allocation of skill points. The older players will always object that this isn't true, even though they all play the same kinds of mages, mimics, and shamans. It's true these guys can king anything, but this has a lot more to do with their unlimited access to endgame loot in party houses that have been in operation since the Bush administration and their decades of experience than the remarkable balance of the game. You really need to have a willingness to learn from other players to be successful. The reality is, though, that most players do not have that and prefer to "experiment" -- over 90% of these people are gone in a month.
You could say the skill system issue exists with lots of other roguelikes and it's probably true. But you can really see the issue vividly by watching tomenet players come and go, building terrible characters for a couple weeks and dying consistently around levels 25-35. Cutting down on useless skills (e.g. swimming, the nature school, etc.) would be a start.
There are many other ways in which the apparent features of tomenet fail to deliver a deep gameplay experience. For example, a lot of newer players are impressed with the size of the world and feel it would be interesting to explore it fully. This would be true if you were playing zangband, which sometimes does generate interesting wilderness. In tomenet, the world is large and empty. There's a handful of towns with dungeons and these with a couple of exceptions are the only dungeons you want to go to. There are others scattered through the wilderness, but most of them have goofy rules, like no word of recall, only down staircases, etc. These predictably get very little play (except the ironman dungeons immediately outside the first town). The rest is mostly featureless. Not a lot of monsters, not a lot of interesting terrain. Travel is slow and uneventful (unless you have a high level character, then it's only uneventful).
Not that you'd want travel to be eventful. It used to be you had to walk about 20 map sectors to get from the first town to the second town with your crappy level 25 character with no speed bonuses and probably not much ability to survive a fight with anything much stronger than a pack of orcs. This mind-numbing journey would take about 15 to 20 minutes. It had to be repeated for every single character you made (unless you die before level 25, of course). It was a blessing that the only thing you ran into were trees that made it so you couldn't just shift-move (run) from Bree to Gondolin, but had to babysit your character, maneuvering around each thing you hit into and hitting shift-move again. If you actually met anything interesting on the way, you'd probably be bored for 10 minutes then die suddenly to a mature dragon.
Note: you don't have to do anything special to get to Gondolin. There's no quest or item needed and there's no way to get there other than walking. All you need -- and it IS required -- is the willingness to waste 15 minutes staring at a field of dots and pound signs going by.
This brings me to the second basic issue: developer culture. These guys just aren't good game designers. The game is full of tedium. You start with the angband variant's ten kinds of fire and associated resistances (fire, chaos, nexus, nether, shards, etc.) and the great fun of sifting through thousands of pieces of equipment to get the combination you need to resist all of them (remember, you're really playing with fire, so to speak, if you don't have all the resistances at once, because even if the thing you're fighting now doesn't breathe shards, there's no guarantee the thing it summons won't -- and you can be sure you won't have time to adjust your equipment). Fine, that's not really their fault, although they would never consider changing it. Over time, as players get a feel for the game and figure out nice tricks to level, etc. marginally quicker and safer, the developers close those. So you like to farm unmakers? Pretty dangerous, but used to be good xp. Not anymore. Zero xp. You like to farm unique escorts and use a staff of *destruction* to avoid killing the unique? Now the *des* staff knocks you out when you use it -- certain death if anything goes even slightly wrong. Drop rates seem to get worse over time. There's rarely an exciting change. The changes usually make the game worse or make no difference. E.g. new classes that are strictly worse than the current viable options -- who cares? You're just creating new ways for inexperienced players to never figure out the game.
The central mechanic of high level play is scumming. You scum levels, you scum shops, you farm monsters. If you know what you're doing, you don't even want to explore anything. You just want to kill packs of Us. You spend hours and hours scumming black markets, dungeon shops, and the lamp shop for gear. It's addictive in its way, but it's not the kind of thing you want to be addicted to.
You really need to have a love for loot to play this game and a high tolerance for disappointment. Most things that look good (level 49 randart or whatever) turn out to be useless. They aggravate monsters, have an antimagic shield, prevent teleportation, etc. Things all but the second are unusable to all viable characters. The antimagic shield would be acceptable to certain kinds of warriors. Who designs this kind of crap? Just don't generate the item. The joke gets old after the 200th useless randart boot with +10 speed.
The player is needled constantly by the designer in a thousand different ways. The developers are generally unreceptive to suggestions regarding balance and mechanics. They view fairly ordinary behavior in multiplayer games as "cheezing." Many exchanges of items are viewed with suspicion, although in fact there's little enforcement. The developers seem to get all their input from a small group of high level players most of whose characters rely heavily on loot obtained from party houses (e.g. you can check one of their youtube channels to see how each of their characters have a full compliment of extremely rare items, including, hilariously, ethereal or death dragon scale mail -- when all your characters can run through walls because of items your friends picked up five years ago, it's really hard to see why anyone thinks the ranger skill tree could profit from some revisions). The hypocrisy of it is a bit galling. But again, this is probably true of a lot of small scale multiplayer games developed by some guy and a couple of his friends. It is an impediment to improvement though.
Well anyway, this has turned into a somewhat less focused rant than I had intended it to be. There's a lot more to be said against tomenet and it could be put more convincingly. The game just basically fails along a number of dimensions to be a compelling multiplayer online game. (I haven't even gotten into the crappy spell system that barely even pretends to address the multiplayer aspect of the game.) A lot could be done to improve the situation -- making most things that are currently instantaneous not instantaneous would be a good start. But that'll never happen. It's a shame because I think a lot of people are interested in the online multiplayer roguelike concept -- it's been in the nethack FAQ since the early 90s -- but they play games like tomenet and conclude that what's out there sucks and what sucks about it cannot be overcome by a roguelike.
