I don't actually care at all about plastic waste anymore. Landfill it and we're good: it started off as oil in the ground, it can end up as oil in the ground.

Plastic not going into stable landfill is the real issue : so actually consumer plastic is kind of bad like that, whereas industrial plastic basically fine (i.e. infrastructure plastics like pipes).

I'm not an engineer, so I may be wrong, but is it actually possible to build a stable landfill?

Wouldn't the micro plastics risk leaking into the ground when it is broken down eventually? When it rains, the water has to go somewhere and unless you invest in expensive filtration systems, this does not seem economically viable. The micro plastics may even leak into the ground water and spread far beyond the land fill.

Even if we do find an economic way to build a stable landfill that lasts a few decades, it will probably just postpone the pollution to a later generation when it is no longer maintained.

But at least it is better than just dumping it in the nature as many do today.