If Lemmy and Mastodon continues to get popular, we will eventually get Instance wars.
If the descentralization of social networks continue, we will have to prepare for the eventual rise of the instances wars, where people will start to fight about which instance is better and which one is weird to be in and so on, but that's for the future of us all.
The problem with transitioning from YouTube to PeerTube is that without a critical mass of users it's just not worth it for creators. But without creators the users won't go there, because there's no content.
Lemmy has that problem to a much lesser extend because this kind of platform is way more focused on the interaction between users. Or put differently, everyone is a creator here.
A tool that uploads and updates videos across multiple platforms while syncing descriptions, tags, etc is something that would be incredibly handy for creators while also being something that PeerTube could piggyback off of. "Why not upload my video to another platform I've never heard of? It can only lead to more exposure."
You are right. Lemmy and Mastodon are user-centric while Funkwhale or Peertube are more on the artist/creator. For this reason I encourage people to use these sites, supporting artists who decide to use these platforms.
I have been trying to browse Peertube every night to find a few creators to subscribe too. You are absolutely right. On many instances, it is a ghost town.