But I feel like that analogy is completely wrong. It's more like finding someone who only likes to play baseball but doesn't like soccer or football or tennis. We don't think that's strange or sad at all (well, except for the folks who hate baseball) - it's just they like what they like and they don't like the feel of other sports.
Heck it's even true of viewing sports. The only sports I actually enjoy watching are basketball and soccer. Everything else is pretty boring to me - is that sad? That I can't appreciate the back-and-forth nature of a really good tennis match between two pros? Maybe to someone who is a "sports enthusiast" or to a tennis fan, but to someone who is a basketball fan and that's all they like they'd just be weirded out that I also like to watch soccer.
Okay. Sports. WotC is the NFL and D&D is American football. Fine.
Imagine you have fans of American football say that they can play non-American football (aka soccer) just fine by simply changing the rules to American football ever so slightly
and it will be good enough and close enough to work. Now try that with hockey. Poker. Billiards. Bowling. How about sumo? It's all the same, right? Just tweak the rules a bit and it's close enough. No, it really...really...isn't.
"But I like American football and I think it can do just fine at replicating sumo because I like American football so much."
Again, it doesn't make sense the way people treat D&D. It's not a universal system and it can't be made into one without stripping it so far back that it becomes unrecognizable as D&D. There's nothing wrong with liking D&D, but it is incredibly silly to think that D&D can do everything. It can't. Just like American football isn't a good stand-in for sumo if you just tweak the rules a little bit.
ETA: Now, taking that wider, to the RPG industry. Imagine that the NFL was so utterly dominant that other sports effectively didn't exist. To the point where they all switched to the rules of American football, but only ever so slightly tweaked the rules to sort of replicate the sports that they were doing before.
"No, it's fine. No, you don't really need the helmet, pads, and jersey to bowl. It's just that American football is so popular we have to adopt their rules to get any viewers. So it's fine. I know it's hard to get a sense of balance with all that extra weight, but practice more, you'll get used to it. The numbers are way up!"
The dominance of D&D so wildly distorts the industry that people can't even recognize how wildly it distorts the industry.