I think I just bounce around too much. I don't tend to stick with a game too long.
And I'd guess this is likely the culprit behind your problems. Any game that doesn't show its entirety to you from the beginning is going to require some amount of experience before you understand "how to play". (Even games that do this will, although in theory they don't.) One of the more interesting nuances in roguelikes is content depth: that is, features that surprise the player long after they've learned the basics. For some of the more challenging roguelikes, there are really only two ways to get particularly skilled:
1. Read up on the game's literature (spoilers, manual, practical discussions)
2. Get a "feel" for the game by playing it a whole lot, in addition to writing down everything you probably won't remember but seems important
This is technically true of any game: I think it's emphasized in roguelikes because of the concept of permadeath, instilling a sense of "I can do better than that" as you go. Mix in the PCG and, what do you know, you'll have to adapt to every game's uniqueness. It's extremely different from twitch gameplay that comes from FPSs or action platformers, but it's also different from many-steps-ahead gameplay that comes from RTSs or TBSs: one might call it a hybrid of the two, making decisions on the fly while still keeping in mind that you'll have to be prepared for the end-game. It's the kind of things that only comes from intimate game knowledge, and it takes a lot of time and effort to get to that point.
Not that I've beaten any of the major roguelikes, either, but I've only played NetHack and ADOM so far, both of which I got decently far without significant spoilers.