Bacteria that break down plastic already exist, both naturally and synthetically. Optimizing those is one of the most popular student projects in my university. Hardly a millennium problem.
Yeah, okay, sorry I didn't spell out that "in any viable quantity." Last time I checked there were still mountains of trash and oil products at the pump.
What you are saying is akin to saying that humans can naturally metabolize methanol so we can employ humans as industrial formic acid producers.
