Plastics are inert, with no sense of morality. They have many uses, many of which have negative externalities. Some negative externalities are worth it though because the alternative would be far worse.

Ultimately your existence is going to create externalities. Unless you're proposing to commit Hari Kiri what ever option you choose will create externalities. So at some point you're going to have to accept that you are leaving a mark on the world.

I personally believe a few grams of microplastics is acceptable in view of the tonnes of co2 not emitted.