What's wrong with Angband? Just out of curiousity... and if you really don't like it... what's better?
Angband (and many of its variants, though not all) is just a bit too happy about a grindy style of gameplay. Because it creates new levels on demand (just use a staircase) it's got infinite resources. All you have to do is search long enough, and you can get virtually anything without taking any risk. There is no encounter (other than the Final Bosses) that you have to defeat; if you feel overmatched or at risk, you can always run away without consequences.
Angband in older versions (and some of its variants, though not most) did not seem to have much variation or consideration in monster AI. Monsters would pretty much act the same way, within the parameters of their abilities and speed. They were easy to predict and stupid about charging into situations that gave you an overwhelming advantage. They'd pillardance with you, or allow you to hack'n'back, or charge into your ranged attacks down long straight corridors, or kill each other like idiots with arrows whenever one of their buddies got between you and them, or fail to exploit numerical advantage by allowing you to break up packs, or fail to exploit ranged attack advantage by closing to melee range where you could easily kill them, fail to surround you when given a chance, allow you to escape packs by ducking into corridors they could have blocked, etc. So the "right" tactic was almost always to control your encounters using corridors and corners to regulate the number of creatures you'd need to fight at once, and doing so wasn't particularly hard. There were basically about a half-dozen tips, tricks, and tactics that you needed to use over and over again. This aspect of Angband has improved dramatically in recent versions; the monsters are smarter now. But Angband's reputation still suffers for it because a lot of people who got fed up with no-challenge monsters quit playing Angband and never learned that this aspect has improved.
Angband has a very long power curve, meaning hit points, damage per round, etc, have orders of magnitude of difference between starting and winning characters. This arose because when your monsters are stupid (and they REALLY were for previous versions of Angband) you have to give them tons of hitpoints or damage to make them even remotely challenging, and then they so far outclass beginning characters that the @ must also have tons of hitpoints and damage.
IOW, the monsters had to have a power curve that gave them gigantic advantages because the game was balanced around monsters that failed to exploit their advantages. And then the player power curve had to match it for the player to even get a chance to use the tactics and tricks that were the "one best tactic" for defeating all monsters. This resulted in a situation where a character "out of his depth" was basically either hopelessly outclassed (too deep) or severely underchallenged (too shallow). Even the best Angband players could rarely manage survival more than a dozen dungeon levels deeper than their peers at the same character level.
Although the monster AI has gotten dramatically better recently and would allow this to be fixed now (and that might be a good mission for a variant), it would require a really dramatic amount of rebalancing work -- much more difficult than making the AI better.
Anyways; whether any of this is actually bad is a matter of opinion (I've heard people say they like "windshield kills" and exploiting predictable monsters, for example), but a lot of people who like, for example, nethack or ADOM consider it very bad.
Bear