If Marvel Studios made the same exact changes to the classic source material - Twenty something Reed, his wee baseball playin' pal Benji, their (same age!) African American chum Johnny, his Caucasian sister Sue and their bloggin' buddy Domashev, I would be STEAMED.
I would be far angrier at Marvel Studios for screwing up, because I know that at least some of the changes FOX made, such as going with a less established (cheaper) cast and retelling the origin were made for cost savings purposes. This is a cheap rights grab, and while I hate the fact that FOX is doing it I understand the business reasons behind it. Marvel Studios wouldn't have that excuse.
And for those who believe that fans of the MCU will swallow anything that Feige and Company give us, take a gander at some of the other MCU boards one in a while. The Mandarin Twist, Darcy, AOS Season 1, Maliketh, Edgar Wright, Ultron's dad - the MCU gets plenty of criticism.