Why? For me it's the opposite. "Public" is a label for a specific type of audience - everyone with access to my feed/timeline (as opposed to a subset like friends, followers etc). If I block someone, they no longer have access to my timeline.
What you want is a list of friends that you share your posts too, but then you wouldn't need social media if you weren't talking to strangers.
> If I block someone, they no longer have access to my timeline.
Yeah and I instantly think "what if they create a new account" and your whole protection instantly fails.
Blocking is barely good enough so famous accounts dont publicly mock you with all of their followers.