I keep my FB to people I have good relationship now and in the past but may be not actively talking to each other. That's okay, because occasionally we would comment on each other's latest update. Have a positive attitude toward using FB.
I'm not sure but I guess this was what they encouraged? I remember going to places and meeting people, they'd pull up their phone and add you as facebook friends. And you'd accept. Not anymore though.
Also, on the UX front; "unfriend" is a pretty strong word. Just leaves a bad taste when you want to click on it :). And unfollow stuff came out so late that the train had already passed.
That for me works much better. Non the less does FB loose more and more appeal to me. Trivial BS being shoved down my throat is just not valuable to me.
I realise that in an ideal world us humans wouldn't click a button and we'd get the prefect endorphin-releasing content 24/7 but at the moment we have to make a bit of a conscious effort and use the tools we are afforded to make the experience better.
If you enjoy Facebook and want to keep in contact with "aquaintances" just spend 20 mins unfollowing and you'll find Facebook is a much nicer place!
It's nice because I don't have to embark on some great friend list culling as a major event, but I do get to trim the list with some frequency.