I want the 2024 Players Handbook to only list the human race, with a note to consult with the DM for other races that exist in the setting.
The Players Handbook should be as setting neutral as possible, except for popular notions about "medieval-esque" plus the existence of magic.
All worldbuilding needs to be in the 2024 DMs Guide, relating to possible cosmologies, worlds, races, and cultures. Especially the Cleric class in the Players Handbook must not lock these assumptions in.
At the same time that the 2024 Players Handbook comes out, there needs to be a 2024 Forgotten Realms Adventurers Guide. It spells out the cosmology of the multiverse, world of Toril, races, and cultures that are familiar to 2014 5e players now. So, this 2024 FRAG (heh) is a core rulebook, and is where to find the beloved races and cultures, including elves and dwarves, among others.
But the beauty of this corebook FRAG, is it becomes easy to swap in, instead, the Eberron Adventurers Guide, Astral Adventurers Guide, Dragonlance Adventurers Guide, and so on.
Each adventurers guide rewrites any races shared with other settings, so the descriptions exactly match who the races are within a particular setting.
Most importantly, it becomes easier for the DM to swap in a homebrew world. Perhaps the homebrew "adventurers guide" starts off local, with a few sheets of paper with brief notes describing the races who inhabit a particular town. Eventually by the time the players reach level 20, there can be a substantial amount of information about the cosmology and other parts of it.
Meanwhile the 2024 Players Handbook, just has humans, as an example of how a race works mechanically, and a few medievalesque multicultural backgrounds relating to the humans.