It can always be tricky to adapt something when the source material has so much to go off of and thousands of die-hard fans to please. This didn’t stop the MCU from making some changes when it came to bringing comic book characters and stories to life and quite often these have worked for the better as these fans have set out to prove.
Marvel comics have been going for quite some time now, with long-standing characters like Captain America, Iron Man, and Spider-Man etched into the comic book communities psyche at this point. That’s not to say they were always represented in one way in the comics, they’ve been going for years and over time they have bound to have changed as society’s values have shifted and different writers have taken a crack at them.