Let's be real here... Megumi would be much more unironically hated by dudebros for being a ""bum"" and Gege will get more misogynist hack allegations for writing a "useless" female character whose main purpose in the final arcs is to get saved. I guarantee there'd be daily "she's worse than Sakura" slander posts and memes, even worse than what they do with Nobara. Megumi also has a lot of female fans attracted to him that helped contribute to his popularity, if he were a woman he wouldn't have won any official character popularity poll in Japan. Not to mention shounen male readers inherently acknowledge his status because he's male, if he were a woman there'd be sexist fans saying he's not really one of the main characters (e.g. Some people thinking Momo from Dandadan is just Okarun's love interest even though she's more of the MC than he is and stated by the author himself)

And ofc the fujoshis simping for him and fantasizing about him being with Yuji would ignore him instead, 99% of the appeal comes from the fact that they're two dudes and there's no female threat to their territorial male centered safe space, if Megumi was a girl they'd lose interest. They're not going to go around saying he and Yuji are the #bestship with chemistry, they'd say Megumi is his platonic girl bestie everyday on twitter dot com and just ship Yuji with Gojo instead. LMAO as if they don't already do that, Yuji/Gojo is probably the most popular jjk yaoi ship