I've tried other RPGs off and on over the years, mostly at cons. I stick with D&D because I prefer the system and the latitude of styles when it comes to campaigns. You may prefer a different system, but D&D has several qualities that make it work for me and the people I play with.Are you talking about 5E? Because superiority isn’t NOT the reason for 5E D&D’s success. The reality is that the vast majority of players aren’t familiar with other TTRPGs and are hesitant to learn. It’s like playing board games with your relatives at Christmas—a lot of the players only know how to play Monopoly (or Clue or Life) and don’t like boardgames enough to want to learn any others. They’re playing the familiar game to avoid being left out, but aren’t interested in doing the work of learning which games they like better.
Yes D&D has a massive head start over most other systems, but saying that people just don't know any better feels dismissive of people's opinions and preferences.