I have far too many unused fonts on my Apple Mac and there are over 900. I use maybe 5. I tried the Font Book app and it shows the fonts, allows you to select them, but if you go to the menu, the option to delete the font is grey and cannot be selected. I tried everything and could not delete any fonts.
There are a lot of foreign language fonts, like Kailasa, which it says is Tibetan. I can honestly say I have never written or read anything in Tibetan and I will never want to. Yet I cannot delete this useless (for me) font.
There are so many fonts like it that I just don’t need, ever, and they must be using storage and memory. I wonder if having lots of unused fonts slows down the Mac. I would not be surprised.