I think if they changed the main Feed back to the content you've chosen to see (friends, groups etc.) it would be a significant improvement, this is still available under Feeds->All but speaking to people most don't know this so they don't use it. I've noticed over the last couple of years a real drop in friends using Facebook and speaking to some of them I think the useless default feed is a big part of that, looking through my feed right now there's almost none of the content I've chosen to follow because it's flooded with posts I have no interest in.
I don't want to see content I've not chosen to follow anyway but the posts it adds are frequently a poor choice, I suspect it's based on what friends have been interacting with however that doesn't mean I want to see them. If I set certain groups I don't want to see as hidden instead of Facebook thinking I don't like that content, it thinks I must really like it and starts flooding my feed with other similar groups.