I don't think anybody is assuming it will stay clean without continued work to clean and improve the root causes of the pollution. Still worth doing.

That is factored into their approach. See https://theoceancleanup.com/rivers for multiple approaches on how to prevent plastic from making its way into the ocean.

Also from the about section of the blog post:

> They aim to achieve this goal through a dual strategy: intercepting in rivers to stop the flow and cleaning up what has already accumulated in the ocean. [...] To curb the tide via rivers, The Ocean Cleanup has developed Interceptor™ Solutions to halt and extract riverine plastic before it reaches the ocean.

Nothing. Philippines is the largest contributor [1], Western countries will clean, Indonesia will continue, it’s a money transfer from the West to Philippines through a garbage medium.

[1] https://www.theseacleaners.org/wp-content/uploads/2023/03/sc...

Because those are two separate problems, and not having a solution for one shouldn't stop you from dealing with the second. If you can remove it faster than it grows, other folks can deal with tackling the vastly more complex issue of getting the entire planet to reduce their dependency plastics.