Turning atmospheric CO2 into plastic probably isn't as feasible as turning CO2 into some other stable form directly. Diverting petroleum production into plastic and them making sure it ends up in landfills rather than the sea[1] does seem like a good thing to the extent that plastic production funges against fuel production, I'm not sure to what extent these rely on separating different parts of the oil that comes out of the ground in the refinery for different uses rather than having one common pool that could be used for either. But plastic buried in landfills does seem to remain out of the biosphere for long enough to be a useful repository of carbon.

[1] Remember, throw plastic away don't try to recycle it or it'll mostly end up in the middle of the Pacific https://hwfo.substack.com/p/an-illustrated-guide-to-plastic-...