In general I'm kinda curious why Brint doesn't get as much hate,
Several reasons.
Gays are a minority. This instantly means less people are attracted to or care about Brint.
A lot of people on this site are into NTR and he's a literal Bull.
For people who are straight and not into being cucked, you can turn him into a chick like 10 mins into the game, permanently, at which point he instantly becomes questionablt pathologically loyal to you for no explained or questioned reason.
Brint's actually a nice guy and knowing a guy you like is fucking chicks, as a straight man, is... good for him?
The only reason to care is if you are a woman specifically attracted to him or a man attracted to him and in general people are a lot more picky when deciding if men are hot than women so that's not actually all that likely, especially since he has a bara-bait body but the artstyle sort of ruins that, being fairly cartoony.
Arona also gets a pass on this because you can turn her into your loyal sub or even as a dom she'll usually only fuck around if you click the 'make arona fuck someone' button.
Cait's ntr stuff is mostly seen if you click the afforementioned 'sleep with vivian' button or you wait in town. Not explore. Wait, specifically. I had her in my party the entire game last run and outside of doing that I don't actually remember her sleeping with anyone without being told to. Even when you set up a literal child-grooming sex temple on your doorstep she only gets involved in scenes involving you (wherein she inserts herself without asking until you remove her from the party, pretty annoying). Seems to be something they've been going around trying to edit out. QuinnerQuinnerChickenDinner fucks around a lot with no input from you and he also seems to be fairly unpopular because of this and just how fucking stupid his character is and how much the world has to bend over backwards to justify him.
On top of this Cait intoroduces herself saying 'lmao imma fuck around will dis make u mad' then people let her join by saying no and get mad when she fucks around in a world of whores when she's the actual literal princess of whores so a lot of it honestly comes down to people just being really fucking stupid.