Matthew Monagle cites the slew of folks on Twitter and Reddit who liked the show but thought it should be a TED talk (or framed as something analogous) and observes that Nanette has elicited “a slight backlash from men who think that the special just wasn’t that funny.”
This connects to the part of the show when Gadsby spoke to the men in the audience specifically. I believe she was speaking about how she wasn't trying to aim the entire thing at them. A good chunk of the show included Gadsby's horrific experiences with men as well as how her gender has been mistaken as so, so it isn't very shocking to me that she was getting backlash from men. Just because Hannah was speaking out about her experiences with men, doesn't mean she was talking about every man, but the ones who didn't find it that funny were probably taking it that way.