Indeed, that's an excellent point. Additionally, the fediverse is already an innovation in and of itself.
Yeah most fediverse projects mimic Twitter, reddit, etc. But they all add the key innovation of federation. Just by conforming to ActivityPub, each fediverse project features a key innovation in its respective niche.
I think part of the reason this doesn't seem as impactful as it could is because federation is still very rudimentary. We are only scratching the surface of the potential that federation theoretically provides. It's a feature/innovation that becomes more useful the larger the network grows, and the fediverse isn't large enough yet for that to become apparent.