For actors, playing different characters is par for the course. It’s in the job description. Most of the time, audiences don’t give it a second thought. Ben Affleck can be both Daredevil and Batman. Of course, it can get a little out of hand at times – we get it, Tim Burton. You love Johnny Depp.
Then again, if an actor works, why not keep them around? Marvel studios loves to re-use actors. It’s done all the time with background actors and stunt people.
There are justifications for extending the practice to more prominent characters. Sometimes the actor wasn’t all that famous the first time, and so they have a chance to reshape their legacy in the Marvel oeuvre. For instance, Michael B. Jordan’s performance as Erik Killmonger in Black Panther has completely eclipsed Johnny Storm in that tragic Fantastic Four remake.
Mind you, there’s a difference between movies based on Marvel characters and titles that exist within the cohesive Marvel Cinematic Universe from Marvel Studios. Sticklers might complain that dual casing creates MCU canon contradictions. Fortunately, most fans don’t seem all that bothered. After all, suspension of disbelieve is a crucial part of enjoying any film or television show, and the comics have a long history of retcons.
For a long time, superheroes were universally revered in their respective universes. Evil was afoot, and most folks were just glad someone was there to help them out of their jams. Sure, you’d get the occasional detractor, like J. Jonah Jameson, the newspaper editor who had it in for 
Effed by the Wind 