It would be pretty easy to ensure kids really are 13:
have a parent vouch that whoever signs up is above 13 and, if 13-18, screen what the algorithm can show.
How would you know it’s really a parent? Parent would need to enter credit card number (often used as a verification system anyway) and would receive a text on a phone number (not the teen’s) and/or an email (parent email) with a code to enter.
Pretty basic. Many online business secure transactions this way.
And yes, SOME parents would go ahead, but at least it’d be a limit for teens whose parents won’t bother or whose parents are aware. 
You gotta start somewhere
In addition, FB (i.e., FB, insta, whatsapp) should be broken because it’s become a monopoly (the problem on Monday showed that clearly) and we have anti trust laws. Remember* the break up of the Bell system? It wasn’t about what people said.
(*from life or history texts 
)
Finally, any toxic product needs to be either removed from market or made un-toxic. That’s on FB.