I see the argument repeated quite a bit. I think it's easy to read this and think "Nothing new, just more of the same, maybe a little worse now". I don't think that's quite right though. A television station can only broadcast 24 hours of content a day. A newspaper can only have so many editions per day, and each edition has a limited number of pages. The same is true of television and radio. But the common factor among all of them is that there is a common reality that everyone is looking at, and there is scarcity because of that: the publication has to choose what will appear each day to the readers/watchers it serves.
The ideal formula is to draw a large group of people in with really engaging content, and then show them advertisements that are likely to be effective for the group of folks drawn to the content. This presents a three-way tradeoff:
1. Write about stuff folks want to read about (but don't make it so outlandish that you ruin your credibility!)
2. Show effective advertisements alongside that content (but not so much you drive them away!)
3. Show enough variety to draw in a large crowd (but still know your target demographic!)
Newspapers, magazines, television, and radio all faced this dynamic and had to make the right tradeoffs to survive.
But there is no common "Facebook" published each day. We can't say "Hey, did you see the top story today on Facebook?" Each article can target a tiny segment of the population and be designed just to keep only those folks engaged. And there's no need to tie a particular advertisement to a particular piece of content, advertisements and content can be selected in realtime based on models of the user's behavior. And drawing in a large crowd is easy, since there's content and advertisements for every tiny group that any entity is interested in targeting. The scarcity that forced reasonable tradeoffs in other mediums simply isn't present on social media. This is a huge difference that isn't captured at all in the "optimize engagement by any means necessary" argument.
Put another way: the problem isn't that incentives are different, it's that the tools available now remove scarcity that previously shaped the entire industry.