It's also chemistry.

As long as we're using natural gas, there be a surplus of cheap ethane and we'll indirectly subsidize plastic, since making plastic out of the ethane puts that waste product to use (by creating plastic waste instead).

I know it's fashionable to blame capitalism for everything which is wrong with the world but it's the people and governments who don't care about the pollution and think that's it's fine to throw garbage on the ground or in the river instead of disposing it properly. The Soviet Union did a fair amount of damage to the environment, despite not being a capitalist country.

Update: a small grammar fix.

it's largely because it's being dumped or littered instead of being disposed in a garbage can.

it wasn't that long ago that most daily use goods were sold in reusable glass bottles, jars, paper bags. Clothes, shoes, appliances, furniture was durable, lasting multiple years, sometimes even passed on between generations. Then, late stage capitalism decided to optimize the hell out of everything, told us that glass is too heavy for economic distribution of goods, paper not hygienic enough and that we need internet enabled toasters. We now end up drowning in plastics, forced to replace cars, heavy appliances every 2 years but most of all are seeking weird solutions and feel good stories to solve this, well in line with the principle of the orphan crushing machine.