It isn't that. it is that people think, for soem reason, that they are supposed to like D&D because it is D&D, and when they don't, they don't know who to process that.
Last time I checked I don't have people shackled to my table if they don't like the game. I've been playing for a long, long time and occasionally people do drop out because D&D just isn't for them. People have a lot of demands on their time, I think you're vastly overstating the issue.
When you are talking about good games that are lesser known or played, no one feels compelled to liek them. if you don't, you don't, and you just move on. but twith D&D, we feel like we have to explain why we do or don't like it, and then defend that against those with differeing opinions.
If someone tries out Daggerheart and it isn't to their liking they probably just go play something else and don't continue to post to that game's forum instead of doom-posting forever on a game they apparently hate.
TTRPGs, as a industry and hobby, would be better off without D&D for this reason alone.
Considering that D&D is the best selling RPG and has had record growth over the past decade I suspect there wouldn't be much of a TTRPG as an industry or hobby without it. Meanwhile there are a whole lot of us who play because we ... gasp!!! ... enjoy the game and have fun playing and don't feel compelled to like that game because it's D&D. If 5e had not come along, I may have gone back to an older game but most likely would be playing something else or gotten more invested in board games. There is no magic to the label, no guarantee of success, no anticompetitive practices by WOTC forcing other game companies out of business.
A lot of people just happen to like playing the game and if you don't I wish you luck finding something that does work for you.