I hate to be that guy, but there's already a thread on the exact same page as this one all about calling people wrong and dumb for liking/disliking permadeath.
I like the tension of permadeath. I think it really is a strong factor that contributes to what's enjoyable about roguelikes. And I think it would be interesting to talk about other ways to carry similar tension into a game without having the start the game over entirely. Come up with new ways to do things. Maybe none of them will be work as well as plain old permadeath, but it'd at least be interesting to think about, and maybe someone'll come up with a cool idea that'll make a cool game.
I mean, I know you can't dictate how a thread you start is gonna go, and things always derail, but it is just ridiculous how almost every thread on this damn forum eventually devolves into one of a small selection of stupid arguments that never get anywhere because people can't accept that other people like different things. There's room in this world for Angband, Skyrim, Candy Crush, Halo, Mario, Street Fighter and Madden. There's sure as hell room for games with permadeath and games without, doesn't mean everyone has to like both or either, doesn't mean people who don't like what you like are to be "pitied," who gives a shit. Care about something that matters.
Anyway, back on topic:
1) The simplest way to avoid death is to not create a game where you can die. If player death is not a feature of the game, then every action in the game can be permanent, and the player can continue to play until the game is finished. Vanguard suggested something along these lines when he said, "your character survives but the town he was supposed to defend gets destroyed." That comment might mean that the game plays like any other roguelike, except when you "die" you get a red mark on your final grade. Or it could describe a gameplay mechanic in which controlling or preserving towns progresses the player toward success in some way.
Interesting. This made me think of Crawl's rune system. You only need a few to win, but getting more is seen as a "better" victory (I've never actually gotten even one, so I have no idea if it increases your "score"). Maybe if you die in an area leading to one of the runes, you could be permanently locked out. You don't lose the game, but you lose the ability to "win" that area and get a "perfect" win.
2) There is a children's game called Telephone. In this game the first player whispers a phrase into the ear of the second, who whispers the phrase into the ear of the third, and so on. The last player hears the whisper and announces the phrase. Invariably people will mishear the phrase and whisper something wrong to the next person, and by the end, the phrase is completely different. What makes this game interesting is that failure creates fun. If everyone always succeeded, and the last player always repeated the phrase exactly as it started, then the game would be terrible. Instead of punishing those who fail, the game's enjoyment comes from seeing how the players' actions caused the outcome.
This principle might lead us down countless paths of roguelike design. How can player failures create fun in the game? Many existing roguelikes allow the death of a player to affect the player's next playthrough. But what more can we do? What if failing resulted in your character's items being randomly switched around? Or what if failing altered the player's path through the world itself? We might imagine a game whose path to victory appears straightforward, but upon failure that path is closed, and the player is redirected through corridors that they never knew existed.
I've occasionally thought about a game which uses some of these ideas. In this game, the player would control a diety-like character who moves throughout a randomly-generated world, attempting to accomplish a randomly-generated goal. The player would have no fear of death, but their actions would affect the various NPCs throughout the world. When the player's goal is finally accomplished or failed, the final state of the various NPCs could be inspected to see how your actions have affected the populace. I don't know whether this vague idea could become a fun game, but I will like give it a shot at some point.
That would be pretty interesting. But it'd probably be a pretty huge project, either to make all the different outcomes by hand, or to make a random generator good enough to make the outcomes interesting. It definitely sounds like it'd be a good game if done right, though.