Avengers: Endgame - 9 Huge MCU Problems It's Created

7. The Avengers Can Now Solve Every Problem With Time Travel

Surely the biggest problem with introducing time travel into any franchise is that it is the creative equivalent of opening Pandora's box - once that element has been introduced, it can't really be taken away.

Every time something catastrophic happens, fans are going to ask, "Why don't they just use their time machine to fix things?", and it's likely to become the new, "Why don't the other superheroes show up?" that plagues most of the solo MCU movies. Hand-waving that the Avengers have a freaking time machine, however, is a little more credibility-straining.

Given that Tony Stark (Robert Downey Jr.) and Bruce Banner (Mark Ruffalo) were able to crack time travel relatively quickly and the machine isn't dismantled at the end of the film, there's going to need to be an iron-clad reason that the heroes can't go back in time in future movies.

Either we're going to get a ham-fisted and unsatisfactory explanation - possibly one related to Pym particles - or Marvel is straight-up going to ignore it, which would be especially terrible.

To put such powerful technology back in the box after centring an entire movie around it has the potential to come off as incredibly disingenuous, short of a clever solution that fans haven't yet thought of.