Evan's talk is a really good companion to mine, where he offers a lot of examples of apps that are missing from the ActivityPub ecosystem but also talks in more detail about some of the incentives that big corporations have to chase ("engagement", for example) that community-based social software providers simply do not.

https://conf.tube/videos/watch/c79457a9-aae5-47dd-8731-617e6b09fe06