I go on Anidb and look at the cast list and if all the main characters are male or all female there's almost an 80% chance I'm not watching the show off the top. JoJo is a double whammy cause that art style and how flamboyant it all looks really puts me off and it's a bunch of dudes.My brother.
Brehs come through with the zestiest of wild mango and I'm just in the cut.
Part of the reason I've never watched Haikyuu even thought it's very highly rated.
There's only a few times I've broken this rule:
(Cast is pretty much all men)
Major
Akatsuki no Yona
Saiunkoku Monogatari
Hana yori Dango
(Cast is pretty much all women)
Claymore
New Game
Comic Girls
Gabriel Dropout
Love Lab
Keijo
K-On
It just always comes across as unnatural that you have a cast of many characters and you mostly exclude an entire sex of them. Some of these shows literally have like one character of the opposite sex in the main cast and beyond that it's all the same sex. Almost all those girl only cast shows minus Claymore are all comedies and the male only ones minus Major were all reverse harems.