Engagement goes both ways, if you don't care about other people's content then most likely they'll won't care about yours (except if you have a shit ton of hive you're curating with).
Sometimes I have to go off hive for a week or two because I've got quite a lot to do. Whenever I come back and see my account without meaningful notifications, I realize you only get the value that you give.
Sadly I don't think anything can be done for people who shitpost as you call it, because a lot of them are quite older accounts and some might not put in as much effort as before since the curations keeping coming in.
Engagement does go both ways for sure. It is frustrating when people won't even respond to the messages they get on their own content.
Something can always be done. It isn't without its risks though :)