I think the issue is that production of plastic seems to be problematic in and of itself because it's so difficult to get rid of. Especially at the enormous scale we're doing it (a single use fork made of metal would be ludicrous).

Contrast to say, very small bits of sawdust or rocks or metal filings or whatever making their way into wastewater. I'd be interested to know the behaviour of other 'pollutants' i.e. materials that aren't especially toxic but modify the environment regardless.

You can't rely on it all being recycled by virtue of it simply existing - we seemingly don't have a solution for microplastics in clothes for example, but also, every item of plastic litter is in the environment "forever" - imagine 200 years of people chucking the odd thing out of the window, car tires, carpets, etc.

So whilst this seems to be a good solution for recycling, it may not be a good idea to allow plastic use to continue ballooning, and if you look at it through that lens we don't actually want to make disposal too cheap.

All of what esotericn said, plus oil and by extension plastic is a limited resource, it makes sense to reuse it, so yes I would say it is superior, plastic is equivalent to plastic. Co2, heat and a bit of residue, not so much.

I know human nature though. Once that shiny expensive incinerator is built, people will want to use it, for everything, and they'll rebrand it 'smart' incinerating so they can tell themselves its the 'good' solution, and pretty soon we're using more plastic than before, and releasing more co2 than before, so my support (which I do have) is very measured.

I was explicitly talking about plastics made from non-fossil carbon. Why is recycling those inherently desirable, over and above raw economic reasons (if any) for doing so?

Apologies, I thought you were talk about normal and bio plastics.

I covered bio plastics with

"Obviously the calculations change once bio plastics start to take over"

I was talking about plastics made from non-fossil carbon. These aren't necessarily "bio". For example, carbon from atmospheric CO2 can be converted to ethane by various processes, and then on to various plastics, with no biological steps involved.