The bugbear: I HATE changing goblinoids to Fey. This is a change for no reason that I can see. It is one of the only places where WotC is actually inserting lore, but it's intrusive in that it changes long established lore in a way that has mechanical consequences. Yuck.
I dunno; I agree it could be ‘change for change’s sake’, but while it does go against established lore, I see some opportunities in it.
First, it creates a clearer narrative distinction between monster humanoid species. It’s good to have something to strongly distinguish goblins from kobolds, from orcs, and from gnolls. In AD&D, they were all just different species of monsters to kill because they were evil. Since then, each has gained stronger distinctive backstory.
And perhaps it’s just because I had Ridley Scott’s Legend on recently, butI can see some real narrative/story building inspiration from goblins as (dark) fey.
I’d look to tie fey goblinoids to Wolfgang Baur’s shadow fey.
To be more specific, I’m looking for narratives for starting my 12-yr old son’s first adventure. And I’m thinking about the sunless citadel. This fey tie seems a great way to tie together the evil druid, the goblins, and the twig blights.
Throwing in a lot of color about a shadowy blight upon the land, it seems far easier to justify an adventure into the sunless citadel, and to justify battling against the goblins as dangerous enemies presenting a serious threat to local civilization. It also clearly distinguishes them from the less dangerous/threatening kobolds of that adventure.
(And we are free to ignore any monster changes which do not inspire us.)