It could be done if peertube used a scheme like BitTorrent. We are approaching a time where enough users have sufficient upstream bandwidth for video.
But then, even without hosting costs, creating videos takes much more time and effort than writing a short text.
A long time ago I read a paper how to mitigate this. Without remembering the details, the idea was: 1. One peer never holds a complete file, only parts of it. 2. You need a key to find all parts of the file and get them in the right order. So Disney can only accuse you of having an incomplete and unusable part of their movie.
But copyrighted material is only one issue. Do you want your hardware to be used for distributing depictions of sexual abuse, or inciting hatred and violence? Any YouTube replacement will need strong moderation tools.