On the other hand, Tumblr is supposedly working on ActivityPub integration, and that could become a major Fediverse player with the ability to replace Mastodon.
But it is true that all these different type of servers have different specializations as to what type of content is easy to produce and distribute on them. A further intriguing aspect is to federate with video, image or audio sharing servers (peertube, pixelfed, funkwhale).
From what I can tell by the comments on this article, WordPress has implemented ActivityPub for publishing posts, but you can't actually follow other people. Maybe the next update will fix all that, but no client app will ever be able to compensate for unimplemented APIs like that. Comments do federate, but it's not as "social" as most of the Fediverse.
In such scenario search engines would also play a bigger role because if people are hosting videos on 50 different services instead of just Youtube, you need a separate search engine which crawls all instances.
I think the current fediverse servers like Pixelfed and Mastodon are emulating centralized services because we are used to how they function and it would be too confusing. If it catches on, then those services can slowly morph and adopt the benefits of the new paradigm
Is WordPress exposing AP to plugins? If so, I'm brushing up my PHP to author a plugin to host a Twitter-like experience on the WordPress site. Let's bring back Pingbacks back! This time, on the Fediverse. I could make dozens of dollars on MRR. Dozens!