>how do you get rid of one?
You simply don't use it?
Log out.
Delete all cookies, in fact block all cookies.
Better: set up browser that it forgets all cookies EXCEPT the ones you want to actually keep. That way google forgets who you are on every browser close.
If a video on yt requires login because age check (TRACIKING!), simply download video via video download sites, some work with age restricted videos.