Landfills really aren't that bad. modern landfills have multiple layers of lining to prevent leaking into water supplies and soil. After they are full, they are covered with earth and can become usable land. Their gases have to be managed (can be burned for electricity or processed in other ways) but overall putting trash in the ground and covering it seems alright to me. The amount of land that you actually need isn't that much too.
The point is that we may not have plastic forever. Oil is a finite resource. An easy, cheap replacement hasn't been found yet. Either we abide by reducing and reusing (where we should be focused), or we should actually recycle.
Hear me out:
Single use plastics are a carbon sequestration technology.
We take oil out of the ground, and instead of burning it we turn it into a solid and bury it again.
Something like 30% of the oil we consume never ends up getting burned. While that's probably not a 30% reduction in CO2 gasses, the price pressure plastics put on fossil fuels is not negligible.