I'm A Banana
Potassium-Rich
FWIW, I think there is an argument to be made that being "generalist" (maybe not exactly in the sense you're using the word here, but in terms of "serving many different game systems") is actually a huge asset for D&D specifically, but maybe leads inevitably to the flourishing secondary market for other TTRPGs.
The idea goes that D&D today has to serve an incredibly diverse audience who all want slightly different things from the game, and so having a broader, less specifically tuned framework helps D&D be more popular because it can be bent in a lot of different directions and works "well enough" that a diverse player base isn't too bothered. A D&D that did these things "better" might steal focus from some of those other things and end up being more narrow in appeal. The argument goes that 4e is an example of this -- a game with a very specific style that wound up having a narrower appeal than the editions on either side of it.
But, the generality of 5e also means that there will inevitably be players who want more out of one specific kind of D&D experience, and find that the more generalist approach feels shallow. There are ALWAYS people unsatisfied with some element of D&D that other groups are just fine with. These players are likely to seek out games with a more specific, tuned focus on the kinds of games they want.
Examples include how OSR games often support "dungeon crawling" as a genre (and often do so with lighter rules than 5e). Or how Draw Steel is a game about fighting monsters, or how Daggerheart is a game about character and narrative. Meanwhile, a broad base of players feel like D&D 5e does a "good enough" job at those genres that they don't need a separate game that focuses more narrowly.
The analogy is that it's like network TV (broadly appealing) and cable (more niche and specialized). A lot of folks will do both, depending on their mood or what others are into or what they want to keep up with. You don't have to do just one or the other.
Heck, I could see a not-implausible future where someone subscribes to D&D for a "season" (a campaign) and gets all the rules and then cancels their subscription and subscribes to another game for a "season" and then returns to D&D or goes to a third game....the same way a lot of folks shift subscription services around today. And some folks will still buy their physical media (books), too, but they might be a little more specialized collector's items.
