lots of medical implants are made of plastic. A great number of medical equipment is also made of plastic. Plastic is used ib critical components in everything from airplanes to powerplants. There's not a lot of things that have the same durability, flexibility, and weight as plastic.

It would really suck if all plastic actually degraded. A better solution imo is to just stop using it for packaging. It's only marginally more expensive to replace it with wax coated paper in the vast majority of cases.