When the OP(top commenter) mentioned building the "Next Thing", I thought we finally are going to discuss about building an alternative to YouTube. But here we are trying to save what's already lost like OP said

Youtube-dl was great and it's huge loss but it seems any efforts in improving or maintaining it will just be harder now. Instead if we could focus that energy on building something robust and resistant to such actions we might actually have solved this.

> I thought we finally are going to discuss about building an alternative to YouTube.

There are plenty of alternatives to Youtube, a bunch of them defunct. Youtube is irrelevant to this conversation; the DMCA takedown would have been equally effective had the copyrighted URLs been from Vimeo or Dailymotion or any other project that dies in a year because its creators don’t understand what makes a video site (and `youtube-dl`) is the community, not the tech behind it.