Individuals and corporations quit caring about the environment; Which, is why there is sewage and microplastics in the sea and ocean.
They did not until environmental regulations forced them to, and they ignore those regulations every time they think they can get away with it.
And individuals are not much better.
For example nothing was done about the pollution of the river Thames until it got so bad it affected the business of parliament.
Oh, far, far longer than that. Everyone is ignoring the fact that fish and other sea creatures also shit in the ocean, and were doing so for billions of years before humans even existed.