I don't see anything wrong tbh. Youtube logo is an image, it is blurry for me as well. Make sure your screen is at native resolution, that could be the heart of your issue, though I don't see much difference between your screenshot and my screen.
Why do you say you are sure that "it is just a small setting that got affected". Has it not always been like this?
I don't see anything wrong, by the way.
because that is what i think... i am not sure if it has always been like this but it just come to my attention the other day while on youtube then i noticed the lettering on the bar up top where file edit etc are and the also appear pixelated.
- Are you, by chance, used to PCs and Microsoft Windows?
Apple and Microsoft disagrees on how to display fonts: Apple believes they should look as close to reality (how the font was designed and what it looks like on paper) as possible (sacrificing sharpness), and Microsoft believes they should look as sharp as possible (sacrificing accuracy).
Fonts look different in Mac OS and Windows.