Wood didn’t rot in the carboniferous era. It used to build up in dense layers that became our modern coal veins.

At some point microorganisms evolved to exploit that vast resource. Now coal can no longer generate naturally and we have to keep wood structures dry or painted lest they be reclaimed by the Eafth.

I don’t know if there’s any reason it couldn’t happen to plastics. We’ve created the niche already, how long until something exploits it?