But we only care about that when it ends up in fish we eat. The fish are dying anyways from overfishing. And even when the fish we eat are full of microplastic we seem to be able to mostly ignore that. Eating fish is a personal choice and all that.

I wish we cared about the rivers and oceans, but as a group we seem to mostly hope that enough bacteria will evolve to eat that stuff. Getting people to do something about the air we breathe is a lot easier (and even then change is slow and with a lot of opposition)