As you mentioned, their customers are advertisers, "users" are there to serve them.
EDIT: before you make the same argument as you made in your reply to another comment, I don't use any Facebook related products and deleted my facebook account over 10 years ago.
I'd also suggest you look into some writing on the attention economy and whales in gaming. All ad supported media is in a race to the bottom to compete for your time. There's a reason why news look like reality shows now.