Even if there were some multi- or omni-functional fediverse metaplatform, I think "what do you want to do" is still a valid question. Some people may want to host a public forum, others may want to host a private family chat, others may want to host and/or share images and video, still others may want to all those things and more with an all-in-one solution. I don't think having a generalist platform would stop others from wanting to host niche or more specialized platforms for their own purposes; it all depends on what you want to do with your hardware.

With that said, I think it would be cool to have better interoperability between services. It'd be cool to have it so that if I make an account on a domain, I could hop easily between all the services hosted there. And it would be cool if it were easier for developers to make smaller services that can run on a general-purpose platform, and easier for admins to add and remove services as they wish, and maintain several services without it being an overwhelming hassle.