My choices from your list are diverse roster and mechanical representation. Balance gets squeezed in as best it can once those other two are handled.
Of course, what I think you're really saying is that WotC is not trying to juggle those three, but rather is focused on diversity and balance, and dropping mechanical representation.
Heh, different editions have made different choices among those three.
5e is favoring diversity and balance, and fitting in mechanical representation where possible.
I wonder what it would look like if we chose balance and mechanical representation? We maybe allow diversity through DM advice and some more radical optional races (like, "We didn't put flying people in the PHB because that changes the game dramatically, and here's why. If you're OK with that change, here's how an aarakocra or winged elf or whatever could work"). People would probably just play unbalanced species anyway, or at least definitely complain that they couldn't play a centaur or whatever, but since each player only plays one character every year or so, I wonder if we'd have much of a problem with it, at least in the PHB.
I think the idea that 5e has too many species is a point with some support, and I also think that the idea that species is part of how you customize the feel of your personal campaign is worth discussing. A game where you play humans, dwarves, elves, and halflings has a very different vibe from a game where you play tieflings, aasimar, bariaur, and githzerai, and that's very different from a game where you play gnomes, elves, pixies, and half-ogres.
My default in 5e is to allow any official species (because I can trust the balance), but I wonder if we'd gain something from empowering DMs to curate that list of species more closely? It says something about your world and your game's intent if there's a minotaur in it or if there's an orc in it or if there's goblins and kobolds in it, or if there's half-dragons and dragonborn in it.
Definitely not the track they're following for 2024, but as much as I adore weird and exotic species, I wonder if we'd gain something by being willing to focus instead on making each species a significant and impactful choice both for the player and for the DM.