Initially: as a preteen, we got tired of AD&D's cruft and were pretty open to trying other stuff - I played a fair bit of MERP and a smidge of Cyberpunk - but it was mostly "Doug found this new game let's try it!" rather than a deliberate choice to play something other than D&D.
When I was a young teenager World of Darkness was just hitting its stride and my friends and I all switched over. AD&D was getting extremely bloated and Basic D&D didn't really allow theory-crafting some we couldn't spend as much of our free time on it. We did develop an attitude about it, but in my defense I was in my twerp years generally. The 90's generally had the perfect zeitgeist for Urban Gothic Fantasy, and Vampire scratched the itch beautifully, even if we were just playing an edgy superheroes game. Werewolf was modern-world D&D but without all the weird cruft of D&D, so it worked for us.
Then 3.0 D&D came out and it was, relatively speaking, a breath of fresh air - more streamlined while being more flexible, a dice system that worked as advertised, and usable monsters already written up. So we switched.
I didn't get to play as much 4e DnD as I wanted, as a lot of people I know had either stuck with 3.5 or PF1, but that was also the period of my life when I had the easiest time trying new games so I got to play Start Wars and Fate and 13th Age and a bunch of stuff at conventions - but for the most part it was a series of competing versions of DnD.
5e's popularity explosion made finding games of DnD so much easier, and 5e is a great robust game for playing DnD a lot of different ways at least fairly well - but at the same time until PF2 came out it made getting a game of dang near anything else much harder it seemed. I have been back to conventions since the plague so I've only really played two games since then: 5e and PF2.