Probably not. All these critters definitely eat other stuff as well. And their non-plastic-eating cousins are probably still around anyway, and would just resume their former role if the plastic eaters died off.

As George Carlin suggested, maybe the only reason why the planet allowed us to evolve was to that it could have plastic: https://youtu.be/rld0KDcan_w?si=0h4qZFzO4S9ijwT0&t=204