It's not just about UI/UX. You need a centralized backend to return recommendations in a reasonable time (if you need to query all the decentralized instances each time, it'll be incredibly slow)... which means that you go back to the scenario where a centralized instance is the source of traffic, decides what is recommended and what isn't.
I guess there's still one advantage in that scenario: somebody can build a competing recommendation service while using the same underlying videos.
Couldn't you store information about all nodes/content in every node? What would change is that the new uploaded stuff just isn't instantly available, only after syncing the new index with all other nodes.
Not really a big problem, because most youtubers, especially the professional ones, shedule their uploads anyway.
Accessing your own node, the one your neighborhood or the next available one shouldn't be slower, the contrary I suppose.
Key seems to be to store the information or index on all nodes and syncing them.
I guess there's still one advantage in that scenario: somebody can build a competing recommendation service while using the same underlying videos.