To be fair, this has happened before, and I understand it was far hard for the bacteria then.

There was a time when cellulose could not be broken down. Trees fell and piled up for ... miles? Anyway, then bacteria figured out how to break it down. (We also got coal from the trees that were burred.) Anyway, we still build out of cellulose. Sometimes we treat the cellulose, sometimes we don't.

Plastic may, or may not, end up the same way.