Chaka
Footballguy
I think people are underestimating the number of comic book geeks out there. Thanos has been around as a major player since 1973. On the surface it seems that Marvel organically conjured this whole event but, IMO, without us geeks collectively losing our minds at the 2012 Avengers post credit Thanos intro, the casual fans would not have come to these films like they did.Most Marvel non- Spiderman villains don't have the name recognition. Even Thanos. Only one who does is Dr Doom.
We're the ones who got our children invested and, as the years went by we got our spouses involved and they told their friends "hey these films are kinda fun."
The MCU mythos is ingrained now so Marvel may be able to pick and choose their future villains and know audiences probably will embrace them. But maybe they won't, maybe they'll look at, for example, Kang and echo the thoughts above. Maybe they say "Okay, apparently this guy is somehow as interesting as the guy who almost destroyed the entire freaking universe. But he really just seems like an explodier rushed sequel like every other franchise."
However the reaction from us geeks to a Galactus would immediately validate the him. And that moves the needle. Sure, we will accept a Kang too but we will collectively need a new pair of shorts if Marvel reveals freaking Galactus.
No amount of Green Goblins will do what Galactus can for audiences.