Google has a habit of intentionally delivering degraded versions of their services to not Chromium based browsers, particularly non-Chrome versions of their browsers (determined by User Agent).
There's a pretty famous example of Google deploying a specific variations of Youtube to Microsoft Edge browsers (back when Edge had it's own engine) and that specific variation would cause Edge's hardware acceleration to break. If you overrode the user agent to present as google chrome, the problematic invisible parts of the page disappeared and everything worked as intended. And what the specific problem HTML was would change just as fast as the MS team could roll out fixes. In effect they were playing a game of "break the browser" against their competitors to force them to apply temporary fixes that would then later have to be removed resulting in unnecessary code churn in their competitors' code bases.
Youtube intentionally degrades the user experience if you use Firefox, at least if you are using a proper ad blocker. And there really isn't much reason to use Firefox if you aren't also using uBlock. So by targeting the users of uBlock+Firefox, YouTube is aggressively degrading the experience of Firefox users. Things I've noticed include:
1. Every video defaults to the absolute lowest resolution (240 or 320) until I manually switch it to a higher setting.
2. Occasional (but fairly frequent) 30-second delay before a page loads (loads enough to show a black page, then just freezes for a while. During this delay, refreshing the page gives the same result.
3. Rarely, interstitial notice pages threatening vague consequences if I continue to use an ad blocker.
They may actually be implementing something on the server side to degrade the performance of connections because they have me flagged as a ublock user.
Can you explain this more? I don't understand what this means.