Hey Julie, I think you are confusing plastic (an artificial product created from petroleum) with rubber (a tree). Yet, both are not transformed by techniques invented by humans, making them very difficult for nature to assimilate.
The plastic itself is not bad. It was not even highly polluting, and the problem is a typical case of over-success.
We wanted a durable product: Now we have something that lasts tens or hundreds of years.
We wanted something economical: It is so cheap to produce that it is cheaper to throw it away and get a new one than to recycle it.
We wanted something manageable, adaptable: It can be challenging and rigid or flexible, opaque or transparent. It can be injected into hundreds of shapes.
Plastic is almost 100% recyclable, it can even be converted into gasoline, diesel, and gas, but we don't do it because it's cheaper to produce them.