Except the decades of materials science research demonstrates that even independently of those economic incentives, scientists understand that although plastics are incredibly valuable in a variety of applications, they’re not perfect (and at worst, actively harmful). This research is being done not because scientists would be sad to think of a world without plastics that provide land owning oil barons their precious return on investment, they’re researching it because science and human progress are what drive us forward. Thus, even in our hypothetical, it’s unclear that plastics (and their ubiquity even in applications where it doesn’t make sense) would win out.

You're missing the point - it's not whether plastic is the best material for a use case, it's about the cost/benefit analysis of using it. Think asbestos - really good at not catching fire, with the slight side effect of royally messing up your lungs.

Plastic is great for all the reasons you describe, but it's really hell on the environment. The thing that offsets that side effect is its cheapness, and that's majorly a function of capitalism/private land ownership/the general way the world is organized right now.

I don't think it's true that plastic is cheap as a function of capitalism, private land ownership, or the general way the world is organized right now. It's cheap because it can be produced quickly and at scale from widely available raw materials. Abolishing capitalism wouldn't change the physics and engineering of natural gas wells, nor of the lumber mills and mining required to make paper and wood.

You mention asbestos, but I'm pretty confident we would not have banned asbestos if we didn't have other comparably effective building insulation materials. (Indeed, it's still used in many poorer countries where people are unable to afford the alternatives.)

> Abolishing capitalism wouldn't change the physics and engineering of natural gas wells, nor of the lumber mills and mining required to make paper and wood.

Of course it wouldn’t, I don’t think anybody would believe this. Abolishing capitalism would change the incentive for collecting and utilising those natural resources, though. It’s a lot easier to justify the made up idea of private property when you’re sitting on a pile of rocks that you believe will make you a lot of money than it is to justify sitting on a pile of rocks that a few people decided might be processed into something that’s a net positive to all of society. I have to wonder if plastics would be as ubiquitous as they are today if we didn’t have a very strong social and economic incentive to drill for its raw materials.

I don't see why abolishing capitalism would weaken the social and economic incentives to drill for natural gas either. Would a post-capitalist society no longer require electricity or heating?

Yes they would require those things, but there would no longer be an incentive to use energy sources that have the marginal benefit of making a few people very rich with the incredible downside of killing our planet.