5. Finally make that Incredible Hulk movie
One of the MCU's biggest missed opportunities is, without question, not making an Incredible Hulk movie led by Mark Ruffalo. If it had been made in the shared universe's prime, that movie would have been a huge success.
The Hulk was one of Marvel's most famous superheroes long before the MCU and yet it doesn't feel like he's had that defining MCU moment. He's also one of the only remaining original Avengers, but fans have not responded positively to him in recent years due to the Professor Hulk iteration of him, and the fact that recent titles have leaned on him for comic relief. There is a disconnect here, and that shouldn't be the case when we're talking about a hero of this caliber.
If Marvel Studios can separate the Hulk and Bruce Banner personas once more and restore the character to his former glory, then there is real opportunity to finally give us that Hulk movie we've been waiting for, especially as the character's most recent appearance in She-Hulk: Attorney At Law certainly suggests he'll get more focus in the near-future.
Of course, we've already had a Hulk movie in the MCU. 2008's The Incredible Hulk was the franchise's second-ever movie and though moderately successful, the saga had not yet found its footing, superhero movies weren't the bankable successes they became in the 2010s and it didn't star Mark Ruffalo in the title role.
While it would have made more sense to do a Hulk movie when the Infinity Saga was in its prime, it could very well be the thing that brings original audiences back to the MCU. A more serious Hulk movie spotlighting one of the original Avengers with Ruffalo in that starring role has real potential. It's just up to Marvel to get it right.
Make it happen.