A blockchain retains a complete, coherent, censorship-resistant listing of what's available on a network in a way that local or federated key-pairs can not.
There is no search all of PeerTube. There is search all of LBRY.
But what's available on the network isn't permanent.
How do you handle when a video stops getting hosted? Does it just keep showing up in search results, and then give an error whenever anyone tries to view it?
And if that's not the case -- if an unhosted, missing video can be removed from the blockchain by adding a revoke transaction or something, then how is it censorship resistant? If entries can be removed from search results when they go missing, haven't you just created a shared database where objectionable content can be removed from search for everyone at once?
That seems strictly worse than Peertube. At least on Peertube if you want to remove a video you'll need to target all of the instances that are mirroring it; you can't just attack one ledger that everyone is forced to use.
You can have a searchable index of content without blockchain. The web has searchable content indexes without blockchains for almost my entire lifetime. What does a blockchain actually solve here? Without a blockchain, at a bare minimum, all you would need is for creators to post signed content to an index, and anyone can verify the content with the creator's public key. Whether a piece of published content has a hash that precedes the previous one seems irrelevant.
Immutability. Once a link gets on the blockchain you can depend on it not changing. The content it points to can go away, but with an immutable index, that is discoverable. Censorship and link rot are more evident.
So if someone uploads a 2 hour version of a rickroll and tags it with the name of the latest blockbuster movie and then takes it offline, there is now going to be a permanent record that at some time there was a copy of this movie uploaded? When in fact that never happened?
How is this in any way better, or even something beneficial?
There is no search all of PeerTube. There is search all of LBRY.