>>355120846
We found out that VRchat is using the now unmaintained youtube-dl, which is now being activly throttled by Google making decoding so slow as to pretty much not work at all. However, videos hosted on people's own domains or on dropbox or whatever work fine, so you should be good. 
The issue is listed here:
https://github.com/ytdl-org/youtube-dl/issues/30075

It is possible to manually change the youtube-dl used in vrchat to a new fork. 
Download one of the .exes of yt-dlc from here https://github.com/yt-dlp/yt-dlp, rename it to "youtube-dl.exe" and place it into "%appdata%/../LocalLow/VRChat/Tools"

I just did this and it works perfectly. Everyone who wants to see youtube videos is going to need to do this unless the VRC devs do it in an update at some point.