Youtube-dl is tool for downloading YouTube videos.
I tried downloading a video with warp enabled: youtube-dl --continue https://www.youtube.com/watch?v=aqz-KE-bpKQ
and it seems to download slow, like 1MiB/s, and without warp it downloads at 7MiB/s
It is probably not selecting the closest server to you when WARP is enabled. This preserves your privacy, but probably isn’t what you want if the server is slow.
AFAIK There is no workaround. NextDNS et al. have a similar issue. Someone from CF can give you additional steps to try.