7. Captain Britain
Thor: The Dark World and Spider-Man: Far From Home's final acts took place in London, while quite a few Marvel Studios productions have shot in the UK (Avengers: Endgame and Guardians of the Galaxy, for example). So, taking all that into account, why the bloody hell has Captain Britain not been brought to the big screen?
It's no secret that Marvel Studios was once concerned whether people would go and watch a movie called "Captain America," so perhaps they just don't think the UK is that cool? As for Brian Braddock, he's a badass interdimensional warrior with a terrific supporting cast who could bring a lot more to the MCU than the likes of Blade, Moon Knight, and even the Eternals.
It's possible the rights to Captain Britain were somehow tied to Fox's X-Men franchise, but now those rights are back with Marvel Studios, there's really no need not to finally put the spotlight on this hero. Alas, no matter how many times Feige is asked and fans of the character campaign, there's still no word on big screen plans for the other Cap.