Just to clarify: some people have pages of house rules, not just minor tweaks. If they want to do that and their players see okay with it, cool. I'd probably think twice about joining a game with more than the typical handful of changes, but that's me.One can like vast portions of a game while also feeling strongly that specific elements should be changed. If someone wants to change 10-20% of the rules, that means they're happy keeping 80-90% of them. This isn't something that should be taken for granted.
D&D is a game with a 320 page player's handbook. As someone who likes playing in homebrew worlds and likes thinking about game design, I don't think anyone could write a 320 page RPG book where I wouldn't want to change more than a page of rules. But I wouldn't take the time to think through and discuss those changes if I didn't like the underlying game.
But some people profess an active dislike about fundamental core concepts of the game. Things that can't be changed with a few house rules. If you've read many threads you likely have seen it. Endless posts about terrible, lazy and basically incompetent design. Longing for a game that simply functions differently, often as a game based on PbtA (Powered by the Apocalypse). Or we're discussing 5E and they want to play 4E or an OSR game. Perhaps some of them are just trolling, perhaps they just feel like venting because the game doesn't work for them. Because when house rules are suggested they complain that they aren't game designers and if the people writing the game would just do their job they wouldn't have to.
So yes, when the problem with D&D basically comes down to the fact that it is D&D then they would probably be better off playing a different game. Because as malleable and flexible as D&D is, no game can be for everyone.