For those of you Critical Role fans out there, I would like to ask, how do you plan to incorporate the lore encountered in Mordenkainen Presents: Creatures of the Cosmos into Wildemount or the wider world of Exandria. How will fey-blooded goblinoids, the Raven Queen's ancient emo elves, Eberron's changelings/shifters, and the alien gith be implanted into your table's Exandria? 

I ask all this as someone not sure of what to do myself. Some of this stuff just hasn't been described yet by Matt or his compatriots (and maybe never will be), and other parts seem almost like they contradict the established lore, like gobbies coming from the Feywild. What do folks here think would be a good way to make things work out? How would you make established CR lore and Mordenkainen Presents: Enemies of the Everything mesh together?

Simplest way to make the more explicitly fey-descended goblinkin work if you want to is to say that the dranassar were elves, or some other humanoid race with fey ancestry. As for the other things that just haven't been explicitly described in the campaigns or sourcebooks yet: Exandria is a big place. There's room for just about anything somewhere in that world. You can say that Changelings are half-fey, half-humans, that shifters are a people blessed by the Wild Mother, or something completely different.

Or you can just say "Yes, goblins are descended from fey in most D&D worlds, but in this world they're not. And maybe there are changelings and shifters and hippopotamusfolk in other worlds, but not here." It's all optional!

Idk very much of anything about Critical Role, but I do know that certain things from other books don't exist in other universes. Changelings are from Ebberon, they can be homebrewed into other worlds, but canonically they don't exist in other worlds besides Ebberon. Every world in the D&D multiverse has its own lore and certain things exist in certain worlds

Edit: so basically if someone wants to play as a Kalashtar or a Leonin in Exandria, you can just tell them those don't exist here  unless you feel like making them exist 

Huh, interesting.  D&D Beyond Races lists only Exandrian Orcs in Explorer's Guide to Wildemount.  However, from what I can tell the races discussed in EGtW track in text to their so-called "legacy" entries.  Looks like Eberron is too.  I don't know what if anything Baker or Mercer have said or may say about this shift affecting their worlds.    

This does seem sort of an oversight in managing the MMM rollout, I'm sort of surprised it hasn't been brought up on the board yet.    Maybe it has, but this is the first time I'm reading it.

I mean, errata could be forthcoming for those books to bring them in line, or I could see WotC/DDB realizing the oops here and/or respond to owners of those books demanding access to the "legacy" races.  Don't really have much of a dog in the fight on this, but it seems like something that would have popped up during review before implementing.  Again, maybe it has.  I know the FAQ or FAQs for MMM have been through a few versions, so maybe this has been actually addressed.

Before I looked at my books and saw the discrepency, my initial/instinctive response would be "specific setting trumps setting agnostic."  So if the official guide to a setting gives specific write ups to how a specific race works, that's how it should be.  So for instance, unless Mercer introduces the Gith into the CR universe, they and their conflicts and mythology aren't going to be a canonical presence in CR ... that doesn't mean you can't insert Githynaki raiders or Githzerai mystics or some unified Gith Mutually Enlightened Co-Prosperity Venture ("GMECPV" which can be translated from Gith as either "Empire" or "Crusade" perhaps) into your game world that used EGtW or other CR texts as its starting off point.  I imagine there are some CRitters who play "strict" with the CR universe, others used it as a foundation to build out from.  

Existing monsters are more a challenge.  I don't know how if at all CR's world interacts with the Feywild or if it's even a party of CR's cosmology.  So having a population that suddenly has "fey" traits is a bit more of a problem.  If you've been doing CR goblins, I"m presuming you've been doing so via Volo's monster, so you got the legacy race or homebrewed off the book themselves.  If that was the case, leave them, unless you see some interesting possibility for your game to "go there" and follow the goblin lineage into Fey origins (I sort of did this in my own homebrew setting when the Fey Hobgoblin was first presented, or rather if the game ever goes there, Archeron is going to get shaken up a bit when Jareth finally figures out the way to open a portal and save his people from millenia of martial servitude ... I'm also in the market for homebrew dance party rules).

As a DM I'd probably take it up with my table and think about how to retcon the changes if the new races were to the game's liking.  I got a feeling a lot of tables are going to start becoming a lot more idiosyncratic as folks pick and choose ingredients from competing texts ... I don't think that's a bad thing either, because D&D fundamentalism insofar as lore isn't a thing, or at least a thing to be taken too seriously.