Wouldn't (fully) burning all single-use plastics effectively make them no more long-lived and problematic than burning crude oil at sea? I know that's a low bar, but it seems like at least you're getting two uses out of them at that point...
Modern landfill is highly engineered and extremely stable: what goes in there stays there.
Plastic starts as oil in the ground. Replacing it as solids in the ground isn't a problem.
Source: I did a bunch of research on rocket mass heaters (think rocket stove, not missile engine) when I built one.
Put some filters on top of the power plant exhausts and it's clean enough to build a ski slope on top of it.