They are a huge problem for non-emissions reasons.
Also, if you live in a major western city, especially a non-coastal one, your garbage is pretty reliably ending up in a landfill. 90% of river-borne plastic pollution comes from just 10 rivers, all of which are in Asia and Africa: https://www.weforum.org/agenda/2018/06/90-of-plastic-polluti...
This is not a get-of-jail-free card to the rest of the world, but it does change the nature of our responsibility— in particular, it means that individual action is almost entirely worthless. Because the issue in the west is not the trash, it's that we're culturally exporting a single-use lifestyle that creates all that mess when it is imitated in places without the pipeline in place to manage the waste. So what is needed is a collective cultural change in order to alter what we export via our media, and the actions/expectations of our politicians, celebrities, tourists, etc.
All the more so if the plastic objects are mostly buried alongside other plastic objects where they can be dug up and reprocessed later on as the need arises.