Not really. They have a lot of bits and in-jokes which are going to seem incomprehensible to anyone from the outside, but most of them are pretty chill if you engage in good faith. It’s like a lot of tech communities; if you don’t do your research and ask intelligent questions, you’re likely to get told to RTFM.
As an old school doom mapper from the 90s, it absolutely isn’t. You build a room, apply F_SKY1 to the ceiling, and that’s it. The engine renders it more like a wall, but it’s not a traditional skybox in that it doesn’t exist in the level geometry outside of the room it’s applied to.
https://doomwiki.org/wiki/Sky