Your concern seems another variation on the old complaint of "They're telling me how to play my game!" But they're not. You are entirely free to construct and use your own cosmology, or to take a D&D cosmology and use that, tweak or interpret it as you see fit.
The Default Effect is
huge. To dismiss it by saying "you can always change anything you want!" means you don't appreciate how actually huge it is. This isn't about a rejection of authority, this is about D&D being a game for each of us to build and create with as we see fit, or about D&D being one particular game that has a specific flavor of multiverse/dwarf/goblin/etc. A Default Dwarf puts it firmly into the later camp, even if the Fun Police ain't around. And that's not what D&D is to me.
Hussar said:
I think a question you have to ask is just how granular do you need the differences to be? How, exactly do you mechanically differentiate one dwarf from another? How much do you need to distinguish one from another? A halfling, a kender and a cannibal Athasian halting are standing side by side. How different are they from each other physically? Do we need different stat bonuses for each? Different abilities? Or, can we simply use culture and flavour text to differentiate, and maybe a tweak here and there?
I'm coming at this from this perspective:
There is never any such thing as "generic". All lemonade is local.
Athasian dwarves are specific to Athas, and have a specific relationship to their world. FR dwarves aren't the same, and they have their own specific context and setting. Dragonlance dwarves are different yet again from each one of the above, with their own nuances that separate them out. Greyhawk dwarves are different yet again. Planescape dwarves? Different again.
They share superficial similarities, sure (perhaps a great place for solid, adaptable, broad, elegant rules!). They're not mutually exclusive (I could play a Greyhawk dwarf in Planescape!). They're not the same thing. If I play a dwarf in Dark Sun I've got a specific play experience I'm trucking towards that is a different play experience than if I play a dwarf from Greyhawk. If I'm in a game with both a Greyhawk mountain dwarf and an FR shield dwarf and a Planescape dwarf from Mount Celestia, I expect those three dwarves to be distinct, to have their play experience be unique, because they are unique creatures with unique skills and abilities to bring to the table.
That context should shine through in D&D the rules for playing these creatures being different.
It's not just biology, it's a combination of biology, society, environment, genre....
context. Lose that context and you wind up with watered-down dwarves that don't deliver a unique setting experience. You lose what makes Greyhawk dwarves interesting and distinct from FR dwarves.
That context is also important in D&D being a game of imagination and creativity: it keys you into the fact that the dwarves that are in your game are also unique to their specific context. There's no canon they must adhere to. There's no mechanics they must absolutely have. They are yours to shape as you see fit for your world.
Or you can just grab a dwarf or three that brings with it the context you want, and plunk that down in your own game.
None of that mandates sprawling blocks of repeated stats and figures, it just means that you need to be specific and local when talking about your dwarf.
And that's just
dwarves, arguably the fantasy race with one of the most consistent portrayals across multiple different companies and iterations! If you don't look closely, a shield dwarf and a WoW dwarf are pretty much the same thing. But when we're playing D&D, we are making whatever game options we choose work for our own local area, in the same way that WoW dwarves work for WoW and not for other worlds/universes/etc. D&D dwarves (and cosmologies and whatever) need to work for
each of our individual tables. That means that the millions of minor variations that make your game distinct from mine are actually really vital to making our experiences uniquely suited for our tables.
I'm willing to believe there's stuff I'm overlooking. My mind isn't set in stone. Wyatt mentioned there were "some problems" with a 3e-style model of the planes that allowed for different cosmologies and different multiverses. I'm willing to listen to what he thinks those are (and I'd hope that he'd be willing to hear other ways of solving those problems!). He thinks it's for some reason really important to homogenize the differences between D&D creatures? Okay, why? I'm not an easy sell on this, but I'm sure they're thinking about this more than I am. Tell me how this is going to be better for my game.