Your wish comes true, in 3 years activitypub is just another victim of EEE.

Wish granted. Never again shall children avoid their parents on social media by switching platforms, because now they’re all interoperable.

Granted. You no longer need to go to c/insanepeoplefacebook, it comes to you.

Granted. When a big sociat network publishes plans to integrate ActivityPub, many instances defederate it and those that don’t are blocked by the others, effectivaly making it a walled garden again.

…Oh wait…

Granted. There are now 15 competing standards to integrate activitypub, and they are not intercompatible

Granted. Effectively a ddos for all instances federated with Facebook. Only Facebook survives.