I get they want to work against ad blockers, but as a Premium member I really wish there was an easy way to watch a video without it polluting my history or recommendations. I don't want to watch ads just due to that.
Account Switcher > Turn on Incognito. (Not the chrome incognito, but YouTube incognito)
IIRC i stopped using this because it takes way too long to toggle on/off and another crucial mistake they make is that YouTube acts like its chrome incognito where you want full privacy and an anonymous browsing experience, I do not want that, I still want to be able to see my own history like my last few search bar queries, I just dont want NEW entries added when in incognito mode. essentially i want read only mode