I know affiliates who have made up to six figures a day on Facebook in some months but they are not going to write about it because they don't want competition.
I have heard Facebook turned their backs on affiliate marketers once the big corporate branding campaigns became ubiquitous.
I have had several ads rejected for attempting to sell Clickbank products (I know, I know - just testing the platform). I had an ad approved, made a sale, and the next day, the ad was disapproved.
It seems they only care about big corporate dollars or local mom-and-pop stuff. No place for affiliate marketers.