I'd say that's not really the problem with Facebook (well it is but bear with me): long ago, at the end of the 90's, it was highly recommended to use pseudonyms on the Internet because `you never know who's who` and well.. it was right and we didn't know what the Internet could really do.
When Facebook/Gmail happened and people were nudged to use their real names... because we need `real` connections. Well, that didn't tipped enough of us. Facebook was the tinder of the day, right ?
But then the whole privacy thing came back to bite us hard (and will bite harder in the coming years).
So we are back to using pseudonyms (which according to my friend's 11yo daughter's guide to the Internet everyone should use anyway) as the default. Except for professional things. We need a professional Internet presence, hello LinkedIn and $name $familyname + 'pro' Facebook account.
Now there was an argument that with everything in the open then people would get more tolerant about other's mischievings and out-of-the-accepted-norm behavior. Big nope as a whole it turned out.
Anyway, youth of today have figured it out years ago and just have multiple personas with different accounts.
With different accounts, not with different circles or different sharing settings. And of course with silly names.
Like you said Facebook isn't designed around the various personas of an individual but increasingly during the last decade the whole Internet community makers (software builders and evangelists and users) were misled on the `true identity` thing and we are only slowly assessing the damage and recovering.
What I mean to say is: everyone was on board with not having various personas. Latest large scale attempt to overcome this failed hard (Google's circles) because people don't want to micro-manage their online Rolodex and it turns out you can't trust Google to respect that firewall anyway (see the cases about people being outed as transgenders).
Only pseudonyms and different accounts can alleviate that and it's going to happen more because most of people will get back to that mindset.