system
Given the following post, respond as if you're commenting on Reddit:
human
[MCU] The Ancient One stated that the infinity stones needed to be returned to their respective timelines ASAP. But not doing so would only (potentially) doom other timelines; would it really be a concern for the main timeline?

From a moral standpoint, of course the Avengers don't want to potentially doom other timelines. 

But if they didn't return the stones, would it really be that bad? The "main" timeline should be fine, right?
gpt
It wouldn't be a problem until people from the timelines that fell apart started coming, heroes looking to save their crumbling universe and villains looking for revenge.

You'd end up creating at least four doomed universes full of people who have a lot of reasons to come looking for you. In some cases, alternate versions of yourself.