A post was created on Reddit's /r/youtube subreddit a few days ago that showed that YouTube arbitrarily loaded slower on Firefox and that switching user agents fixed the problem. For some reason, the all-mighty moderators deleted the original post for reasons not specified.
You can view an archive of the video they posted here.
Source: https://www.androidauthority.com/youtube-report…irefox-3387206/
Pretty much everyone knows why Google is doing this. They maintain the engine that powers some of the most popular browsers right now, and they want you to use a Chromium-based browser so that when they shitcan Manifest v2 (which is what many ad blockers use) in Chromium, you don't have any other options. Firefox isn't Chromium-based, and Google is seething knowing that one of their big competitors aren't bending the knee to use their garbage glowware which they can't control.