Why, when Spelljammer is literally a highway between material realms, of which FR is the kitchen sink now anyway?
Like do you realize you are arguing for making FR the least defined, least unique, anything goes, boring grey mass blob of a setting as if its a good thing?
All races? All classes? All backgrounds? All products? What is FR?
Hard pass dude.
Diversity doesn't make everything a Grey mass of a blob.
Not all races go in FR, Warforged don't.
But HUGE part of the Forgotten Realms story is Immigration, from different places, different worlds, weirder places, and how new folks and old mix with the history of Realmspace and its afterlives.
It makes the Realms no more flavourless then then all the wonderful immigration, organic multiculturism, and cultural exchange makes Toronto flavourless, it's the essence of the community and its soul is in its stories and infinite possibilities.
The real world is a "Kitchen Sink" and that is makes it special, instead of one note and unevolving.