The solution would then be to break them up or do things like require adversarial interoperability, rather than ineffective non-sequiturs like requiring them to ID everyone.
The perverse incentive comes from a single company sitting on a network effect. You have to use Facebook because other people use Facebook, so if the algorithm shows you trash and rage bait you can't unilaterally decide to leave without abandoning everyone still there, and the Facebook company gets to show ads to everyone who uses it and therefore wants to maximize everyone's time wasted on Facebook, so the algorithm shows you trash and rage bait.
Now suppose they're not allowed to restrict third party user agents. You get a messaging app and it can send messages to people on Facebook, Twitter, SMS, etc. all in the same interface. It can download the things in "your feed" and then put it in a different order, or filter things out, and again show content from multiple services in the same interface, including RSS. And then that user agent can do things like filter out adult content, if you want it to.
We need to fix the actual problem, which is that the hosting service shouldn't be in control of the user interface to the service.