It's irreplaceable in a lot of applications. There's a reason we're using so much of it. Even in applications where it can be replaced, doing so would result in burning more fuel to transport the other, heavier material, accelerating global warming. Lose-lose.

It's also likely an uneccessary nuclear response to the situation. I doubt every plastic is as bad, do studies and ban the worst/least useful plastics and work your way from there.

I mean synthetic textiles alone make up almost half of the plastic in the ocean.