And the way I see it the only way around it is cultural indoctrination.

It doesn't have to be a negative concept. It can be as simple as picking up a can as you walk by it on the street, and otherwise having a completely normal life. People with you can then see "huh, I can contribute just a little bit, feel good about it, without going full hippie high-viz jacket and tongs with a trash bag every weekend."

Yes. Small things help. Or at least not making it worse. One doesn't have to be a Greenpeace activist to not throw trash on the street, normal everyday behavior would be enough in this case. If only all other societal problems were so easy to solve!