I think the main problem is that the average Joe/Jane confuses all types of pollution as equally bad. The real, most imminent threat is really CO2. That's what we have to spend the most money/energy on, because it could have absolutely catastrophic consequences in the next few decades.

Plastic in a landfill is just... Stuck there. It's unnatural, sure, but it's not immensely harmful, not nearly on the same scale as CO2, and realistically, in the future, we'll be able to mine it out of there and refine it into something usable if we need it.