Talk about it (worked for the ozone layer and some pesticides), use less (not that hard), support any alternative. And I think this works for any topic. The helplessness is a feeling, hard to assess the impact of individual actions, so why bother? You do what you can/think of and continue living - with a critical mass things will move in the right direction.

Vote for political parties that have it in their party program. Prefer buying products without plastic packaging, this includes bottled or canned products; find markets if you can't find it in your local grocery store. Donate or join up with anti-plastic activist organizations.

IMO a start would be to require that plastic-producing companies accept all their used products back at end-of-life and incinerate them.

Wait for the science to deal with it, or become a scientist yourself. With how ubiquitous it is, it's going to be hard to filter it out of the entire planet, so chances are you'd want to find something to deal with it in humans.

Plus any planet-wide solution risks having its own side effects which may be worse.