I always liked Brendan Behan's quote:

“Critics are like eunuchs in a harem; they know how it's done, they've seen it done every day, but they're unable to do it themselves.”

Critics could be experts of past era who have seen it all and are now seeing the same mistakes being repeated.

Everything that needs to be said has already been said. But since no one was listening, everything must be said again. -- André Gide

Behan's criticism of critics then makes him an eunuch who's criticizing eunuchs... according to his own "logic".

Harems did not had much of heterosexual sex going on in them. Whole point was gender segregation. Eunuch in harem have seen women, but did not seen them having sex with men.