I don't think a fork will solve anything. I'm pretty sure the reason they did this is to cover their asses (don't forget that it was very near to being taken down just a few years ago).
Further, yt-dlp has implemented plugin support, for this exact reason. I think that's a new feature compared to youtube-dl. You can add your own extractors as plugins, wherever you find them. As I remember there are a few plugins that are even maintained by a yt-dlp maintainer.
If you find this to be ok or better, please consider changing the title to let those know about what's happening who have already read the post, because they wouldn't know it otherwise.
It used to work last year 😀 . The debian yt-dlp version: stable@2023.03.04 is giving a different error
ERROR: [Einthusan] 9r1H: 9r1H: Failed to parse JSON (caused by JSONDecodeError("Expecting value in '': line 1 column 1 (char 0)")); please report this issue on https://github.com/yt-dlp/yt-dlp/issues?q= , filling out the appropriate issue template. Confirm you are on the latest version using yt-dlp -U
Maybe you can find some more discussion and the reasoning in their documentation or Github issues or pull requests. I bet this has been discussed before someone implemented it. Maybe there's also a way to restore the old behaviour.
The most likely explanation is that their previous implementation broke due to a website change, and they didn't want to bother with fixing it. People began opening issues for them to fix it, but now it looks like they're aiding people explicitly asking for piracy, so they can't win (and also I'm willing to bet it fucking sucked trying to support that particular website)