What is Facebook?
Actually, my experience with FB (I have an account, but don't spend much time, there), is that it is packed with grayhairs, like me.
I think the younger folks have other venues they frequent.
This is essentially a reverse network effect: because so few young people are on the platform, few other young people see a reason to use it.
We like to throw anyone over 40 into the skip (especially in the tech industry).
It has caused some issues.
The company does have a fairly young, highly-paid, workforce.
I assumed the user base.