I'm exaggerating but it's true that characters like Spider-man have essentially been the same since the 70's. Spidey even had his marriage reset because it wasn't enough like how he used to be. He still fights Mysterio, Electro, Sandman and the Rhino, he still has trouble juggling his personal life and crime fighter life. Outside of some exceptions like Daredevil and current Journey Into Mystery(and I'd like to give props to Invincible Iron Man for developing Tony Stark quite a bit since it started, even taking him away from the Iron Man identity several times) comics are slaves to the status quo. Even when characters do get big changes they're reset by the next writer, and even when they die they come back to life.
Obviously that's an issue you have to come to terms with and get over if you like comics because otherwise there would be no comics at all, but I think with the MCU they have the chance to make things more "concise", maybe is the word? For example, Breaking Bad, one of my favorite shows of all time is coming to an end next year and I think it's going to be better off for finishing it up while it was still great and giving the characters lots of closure. I'd like it if instead of seeing Iron Man recast probably not as well and stretching it out for another trilogy we just saw Tony Stark end as a character somehow so that we all remember him as something very good that can't be replaced easily.
It "cheapens" the character to me when he can be replaced by another actor so easily. And yes I feel this way about Bond too, since less than half of the versions of his character have been any good and one of the best only came about when they basically reset the character and made him more edgy in Casino Royale.