The piece of knowledge that was hidden from you was that the
plastics/petroleum industry lied and astroturfed to convince everyone that plastic bags were a greener option than paper or anything else. And that industry keeps coming up with
more lies to
protect their market.
The simplest "green" solution to the plastic and garbage problem broadly is to REDUCE. That's the first part of the "reduce, reuse, recycle" mantra that has been drilled into everyone's brain at this point. When you go to the store, if you can say "no thanks, I've got my own bag" then that's a few less small pieces of forever trash that will clog up the surface of the planet.