Creators lost any and all rights to anything they created while under contract, and with that potentially millions in royalties from Marvel's billion dollar empire.
Smaller creators have fallen through the cracks.
Image Comics spawned from this practice; it was to make a publisher for creator-owned works so they kept all their rights.
Marvel Entertainment (comics) is for all intents a separate company.
Maybe try to do him a solid come Guardians 3, eh?