I say this as someone who publishes indie games, writes for indie games, etc: the truth is, most people don't want to engage in the kind of game the vast majority of TTRPGs are.
A lot of people want to sit with their friends, talk a little silly, fight monsters, pretend as a character, and experience some kind of story they get to influence and shape. D&D accomplishes this, its the most well known game with the biggest budget, and its super duper mega easy to get into it due to the fan ecosystem that exists. People will run you a game of the "first and biggest RPG" and offer to teach you the rules so there's no barrier to entry.
Not many people want to learn rules of ANY kind, lite or crunchy, especially if those rules are for things like exploring the human condition as you shapeshift through various bodies in Eclipse Phase, or run a meatgrinder of 40 characters in DCC, or engage in difficult logic/logistics management puzzles ala OSR. The market makes that clear. People want to feel a little bit empowered, they want a bunch of help getting into a game, they want to play the same character for a while, and they want to do "the RPG things" (fight, talk, explore, long rest).
I know people will ask me to cite data or rebutt my claim with how OSE and PF2E are sooooo easy to get into, but at the end of the day, most people want what D&D 5E is putting out. It's not my core taste either, but it is the reality of the situation. Avant-garde, experimental, or deeply rich games like Bluebeard's Bride aren't what brings in millions of customers. Magic beat'em ups where you get to be the good guy in a story (probably one of the oldest human stories out there) is what brings in millions of customers.