Because the whole problem essentially boils down to "if it is individually cheaper for everyone to dump their waste into the river, instead of properly processing it, then that is what is the individually rational thing to do, even if in the end everyone loses far more on it". It's washing time and effort on competition, resulting in worse long term results, instead of cooperating together for a better final output.

That's because you're well off in the international context. If you lived in an exploited country where life has been getting worse by many metrics for generations, you probably wouldn't feel like we're "moving in the right direction." Most of Europe and America has benefited from the imperialism of global capitalism.