A yt alternative that worked for content creators to be able to live off it.

How? I'm not sure.

PHP styled forums and Boorus would be cool. I know some PHP forums have recently added activitypub support, but it's still pretty recent and doesn't have much of a userbase.

Also a video platform like YouTube in a way. There's still a lot of issues to solve with that though, like storage and monetization. PeerTube just isn't going to cut it. Realistically if this were to ever happen, it'd have to be YouTube themselves to add activitypub support themselves and let people connect to them.

Ranker.

Flickr

Because Instagram sucks, and Pixelfed isn't really that amazing of a social media service despite having some great photography to gawk at.

I'd also like an alternative to Vimeo since not that many design agencies post their cool stuff on YouTube or even PeerTube (and I'm basically addicted to television branding).

I'd LOVE to see a fediverse and updated version of Livejournal. Private blogging is an insanely good way to make lifelong friends.

Can I choose 'none' as an answer?

Aside from being a difficult concept for non-tech people to grasp, the problem with the fediverse is that it's an absolute nightmare to moderate. Nothing is stopping bad actors from creating their own instance and flooding others with illegal content. Lemmy World and Lemmy.ml have already had incidents where communities have been targeted and flooded with CSAM.

Social media platforms that I do have problems with can't see a good fediverse alternative for these reasons, plus a few others.

YouTube as one such example: the problem is that video hosting costs a lot of money.

YouTube I know some peer to peer stuff exists but I haven't checked it out. Not sure how federation would come into play