>Paper bags do have a larger carbon footprint, but I assume that parent is talking about plastic waste ending up in the oceans
Most of the plastic in the oceans isn't coming from consumer waste[1]. Furthermore, most ocean pollution comes from a few developing countries[2]. Therefore a ban single-use plastics for consumers in developed countries will have little or zero impact on ocean pollution.
The developed countries send their plastic to developing countries to be "recycled" and then it ends up in the ocean. So ultimately, a ban in a foreign land actually can help. See Plastic China.
>The developed countries send their plastic to developing countries to be "recycled" and then it ends up in the ocean
That statement might be broadly true, but I doubt that it's accurate for plastic bags.
For china at least, only around 10% of their total waste is imported[1], so blaming it all on developed countries is questionable. The data is from before the ban, by the way.
I'm not sure what you're implying by putting "recycled" in quotes, but they're not definitely taking the plastic and dumping it into their rivers. They're paying us for the plastic[2], not the other way around. Plastic bags can't even be recycled in most jurisdictions, so it's unclear how they'd be imported into those developing countries in the first place.
Most of the plastic in the oceans isn't coming from consumer waste[1]. Furthermore, most ocean pollution comes from a few developing countries[2]. Therefore a ban single-use plastics for consumers in developed countries will have little or zero impact on ocean pollution.
[1] "Ocean-based plastic originates mainly from the fishing industry, nautical activities and aquaculture" https://www.iucn.org/resources/issues-briefs/marine-plastics
[2] https://www.statista.com/chart/12211/the-countries-polluting...