i personally find presenting a black and white "it's either one way or the other" perspective to be problematic.

yes, materialism and cause and effect etc. etc. agreed on that. it is a thing. interestingly though, as people sit static and just work on becoming more aware of that feedback loop you mentioned it can lead to people trying to not be so much of an arsehole -- through refraining from doing a thing -- because they can see their part in causing things to happen in the world. and that's not just limited to immediate surroundings. i know that i affect everything with every action i do (or do not do).

idealism becomes useful at that point. it can provide people with a set of loose guidelines on how to "not be an arsehole" aka how to not affect everything in a way that's going to cause problems.

the problems come when people do idealism without being aware of that materialistic feedback loop. they're usually doing it out of rule based dogma based on tribalism. sometimes it's "we're better than you are" or sometimes it's "outsiders are not welcome".

caveat: this is all just my personal experience, but i think it would scale if enough people became aware that their actions matter and have profound consequences, so try to not be an arsehole to anyone today