Yeah, sure, Bruce said they can't be brought back. But why exactly? He never explained why and there's actually a very easy way to bring them both back. This is the same way that both Gamora and Thanos were brought back. They just have to go back in time to a different one of the 14 million possible outcomes and grab them and bring them back.

First you have to understand how branching timelines work. For every action, there's an alternate timeline where a different action is taken. Let's say I punch my friend. A branching reality is created where I didn't punch them.

That's where the 14 million outcomes stems from. The one event, Doctor Strange giving the Time Stone to Thanos grew into 14 million possible outcomes. (There's no alternate timeline where he doesn't give him the stone because he knew it had to be done and only would have chosen that action each time.)

There's also no branching timeline with Captain Marvel saving Tony. The first branch is the rat that presses the button on the van to release Ant-Man. There are 7 million outcomes where the rat releases him, and 7 million where he does not.

There are also a bunch of other branching timelines going forward such as Tony not being able to solve the time travel equation or refusing to go back in time.

There are also a bunch of outcomes where Clint is the one to jump, not Black Widow. This would be the perfect place to go back to and scoop her up. It's a failed timeline and she has all her memories and experiences. This way it wouldn't be like Gamora jumping to the present and not knowing anyone.

Tony would be a bit trickier because they'd literally have to wait until the last second to grab him.

The one timeline where they win is because Tony at the end sacrifices himself and does the Stark Snap. But how did it get to one final outcome? It went from 8 to 4 to 2 to 1 as certain actions were taken.

But what was the last branching timeline? I think it was Tony hesitating. I think that in both outcomes, Tony does the snap, but in one, he hesitates. For a split second he takes into consideration that he's going to die, but that's enough time for Thanos to snap before Tony can get the stones away from him.

That would have been the perfect point to grab Tony. Like Black Widow, This verion of Tony would also have the same memories and experiences as OG Tony and this is another failed timeline, as they're all literally seconds from being erased from existence.

The only obstacle this theory faced was that people questioned why should they wait until the last second to grab them? Why not just grab them earlier like before the snap? That way they wouldn't have the pain and suffering?

Well it would be too risky to grab them before the snap because Thanos could get word of what they're doing again and he'd be right back in the future again.

Also if they grab them too early, it's possible that they grab the version that goes on to be the right outcome, they have to make sure that they 100% grab them from a failed timeline. If they accidently grab the version of Tony that saves the world, everything falls apart.

TLDR: Too bad, go and read it.