This assumes that Facebook is something like a dating site, where people are seeking others with a common interest.

But are people seeking anyone on Facebook?

I would claim that Facebook is essentially the "end of point" of a friendship. You are not going to become close to someone through Facebook, just avoid the complete lack of contact that otherwise accompanies having met someone two years ago - where short-term interests can still watch each other long-term.

If people aren't seeking new contact on Facebook, all the algorithms in the world won't help them achieve it.