ActivityPub is a pretty bad example, since it's new. It hasn't had to endure decades of implementations and extensions, like email has. But ActivityPub will be an equal mess given enough time.
Anything that has to be backward compatible for too long will become a mess.
Incidentally, this is one of the biggest complaints from a technical standpoint that many people have with certain Microsoft products.
ActivityPub might be closer
100%
ActivityPub is a pretty bad example, since it's new. It hasn't had to endure decades of implementations and extensions, like email has. But ActivityPub will be an equal mess given enough time.
Anything that has to be backward compatible for too long will become a mess.
Incidentally, this is one of the biggest complaints from a technical standpoint that many people have with certain Microsoft products.