I really disagree. As long as you're not hurting anyone, what does it matter how you have fun with an RPG? You're basically saying that people like me should get out of the hobby, or at least that we're literally having "badwrong fun". Hard not to take that personally.
No, that's not what I'm saying at all. You're putting words in my mouth.
I'm saying that if a GM isn't having fun during play... during the actual hobby we're talking about... then that's a problem. I'm indifferent to the fun a GM has outside of play. If they like world building, and that's how they spend their time in between sessions, that's perfectly fine. If they don't world build at all, that's perfectly fine, too.
But as far as play... the group activity where participants get together to play the game... that should be fun for everyone. If a GM isn't having fun during play, that's a problem. If a player isn't having fun, that's a problem. I'd say the same thing about basketball or poker or any other group activity.
None of that has anything to do with badwrongfun. It's about the absence of fun.
If you enjoy worldbuilding and your players eat it up and everyone's having fun, then of course nothing's wrong. I've been talking about the potential problems with heavy setting lore. I think it often gets in the way of play... the GM's lonely fun supersedes the group's fun. As I said, it can be very self-indulgent.
If you don't think so, that's fine... that's not your experience. But as I said earlier, I include myself in this assessment. This kind of stuff used to be a big part of my game... I was very much a world builder GM and would spend days in between games working on material for the game. And in my case... in my personal experience... my game suffered for it. I didn't realize it at the time... the games weren't bad, necessarily, but they weren't as good as they could have been. They were not as player driven as they could have been, which is something that I've come to prioritize.
My games have improved a lot since I've shifted from this approach to play. I've stopped trying to make players care about the setting I've created and instead focused on play in a way that serves the group activity. It has things for them to connect with in the setting, and places for them to introduce their own ideas, and so on.
If it doesn't apply to you, that's fine. But don't assign motives to me that I don't have and don't deny that this is something that others may want to consider.