Depending on how you count the fediverse / activitystream/pub concepts are now more than a decade old. There have been indeed many AP services around, but practically none - except Mastodon - has seen any significant adoption. That exception is almost certainly because of the Twitter "situation" (incidentally currently boosting also the traction of the unrelated Bluesky/ATProto project) which has created a small window of opportunity. No such window exists for the other centralized social media / adtech platforms and adoption of all other services (video, audio, pictures, forums, events, professional profiles etc.) is therefore minimal.

> Couldn't that be considered a success?

It is actually enormous success given the resources. But when you consider the vast and rapidly growing number of people trapped in the handful of adtech platforms then you must either concede that the status-quo is unchangeable or change strategy.