On one hand, cleaning up plastic pollution is a fantastic thing. On the other, there is a tremendous amount of carbon currently locked up in plastics which is for all practical purposes inert. Releasing that into the atmosphere is yet one more thing that will accelerate climate change.
It also will require a massive shift in our material usage. Bacteria breaking down that plastic bag in the ocean is great. Bacteria setting in on construction, medical devices, or your NES is not so ideal.