A computer protocol is a language. If two or more computers use the same protocol they can theoretically communicate. Like human languages, these protocols have limitations and the things which can be expressed using that protocol only include concepts that are present in the culture which created it.
For instance in Latin, all objects have gender. In English they do not. You can't create a perfect mapping between the two unless you know the gender of all objects - and English speakers will not know this.
This is the reason why multi-protocol systems can't really evolve - unless each and every component protocol evolves. The multi-protocol system needs to embody those things in common amongst all of its components. You can't just add a feature unless it is supported by each and every underlying protocol. We've tried. This just leads to confusion.
It is also the reason why some protocols are inadequate for different use cases. A protocol designed around Twitter interactions cannot express the same concepts as one that was designed around Facebook interactions - and vice versa. They come from different cultures and have entirely different uses and expectations. Twitter is a soapbox platform. Facebook is more of a conversational platform. They can't be made to look and act the same because they aren't the same.
Then you have protocols that were built around cultures that aren't even formally recognised yet. In this case freedom and privacy loving Facebook refugees who want to be decentralised but not bound to individual servers.
ActivityPub may solve the second part eventually and provide nomadic identity, but it's still a Twitter interaction because that is the culture which created it. Ditto for permissions and spam prevention and abuse. That protocol is derived from a culture where privacy and permission didn't even exist and people depend on their site owner to make them safe. This safety vanishes in a nomadic world and other mechanisms are needed. The precise mechanisms needed by the former are completely different than the mechanisms required by the latter.
Because it is a different culture.
We currently have at least four separate (major) cultures present in the so-called fediverse and they all use different protocols for a reason. Those protocols reflect the cultures which spawned them and fulfill the needs and desires of those communities. It's time to stop pretending they can be reconciled.