This always bugs me.
I'm not brilliant. I can write a smidge of code. I do linguistics pretty well but I'm shit at mathematics.
And when I hear people, for example Chris Delay of Introversion Software, say stuff like DF's UI is `impenetrable`, I just have to go "What?" I have all the respect for Chris Delay but it just seems kind of...lazy to say that about DF's GUI and all the systems going on it. The UI is ugly and unhelpful but it's not rocket science. I spent about a day with a wiki article and that got me about 70% of the way toward learning to play DF. That and about half a dozen forts before I learned the things that help make the kind of fort I wanted to run. I single out Delay specifically because they just put out a Prison Architect update where they spend a decent amount of time referencing DF, because the two games are so alike. Similarly my roommate, who is way more of a FPS gamer than he is anything else, is totally hooked on Rimworld. Which is also like PA and DF, just without the scope.
For me the truth is I just got so inspired by DF stories that learning the game to my own satisfaction became important to me, to the degree I did the learning necessary to achieve fun. It didn't take superhuman effort, it wasn't complicated. It doesn't take autism levels of focus to learn. You just have to be able to read, be willing to experiment and be patient.
I think people just often don't say what they really mean when it comes to DF: it's a lot of work to play a video game. Even when you know how to play it, managing all the details is work. Enjoyable work, for those that like DF. What I get out of the hours spent setting things up is rewarding. It made the initial investment of time and understanding worthwhile, mostly because I know it well enough I don't have to completely relearn the game. (Other than, you know, new systems, and constantly having to relearn which keys are different between screens.)
Something a friend of mine once said to me a while back when I first got into DF and I started regaling him with tales of it. "Dude, I wish I was 14 again and had all the time in the world to become master of playing DF. I just don't have anywhere near that kind of time anymore."
Some people simply have the inclination to spend hours and hours on a single game thinking things through and learning as much as doing. A lot of people don't.
If there's one thing that stops me from playing DF more, it's the half day or so of downloading mods for it. I could probably get away with just Dwarf Therapist and a tileset if I'm honest, but there's just too much other good stuff out there to pass on. But that's really no different than when I decide to play Skyrim, for example, where I'll spend at least the better part of a day assembling a mod list and getting them all installed and working.