PLA (the corn plastic) is not really that biodegradable. You need an industrial sized compost heap to get it to break down. Otherwise it’s going to be hanging around a long time just like everything else.
Time scale is clearly an issue with your statement (that is repeated over and over).
If I was, it would be, don’t rely on supposedly biodegradable plastic. Do they really do anything in a biologically inert environment?
https://www.ftc.gov/news-events/press-releases/2013/10/ftc-c...