I presumed from the context of the comment that 'usable' was rather loaded language used to denigrate the built-in Start menu in Windows 10. The interpretation works both ways, however.
Note also that I don't especially consider Classic Shell to be an odd program given that when I briefly worked at Microsoft a few years ago (Win 8.1 was current), my manager actually recommended I install it on my second day there on the company-provided computer in order to retain the classic UI because that group found the Win8 touch UI to be unusable on the desktop.