Excellent points.
I'd argue that most people prefer posts about a certain topic specific to their tastes.
This is one of the reasons my feed is a nightmare - I follow a lot of people who post on various topics but only some of their posts are about something which I am interested in. If there were a more intelligent way of constructing the feed - perhaps as you suggest using tags and maybe even other ways to personalise it, it would make the job a lot easier.