I'm necroing this thread (look last time this thread was used this site literally EXPLODED, I'm toying with fire here) but I do have one idea as to why people don't like fighting inkbrushes that much.
I think a big issue to me is that inkbrushes have always been 180p, even lower in some cases (vanilla brush is literally 150p in s2 lmao), but inkbrush is not a bad painting weapon by any means. Yeah it can't paint very far, but that's not a problem on the maps where it's easy to get behind enemy lines. So every time brushes get behind you, most players I see at all skill levels just farm for special, and pop stamp behind you.
I'm mostly referring to brush nouveau here, killer wail spam isn't as threatening though that kit spams bombs from behind which isn't very fun either. Ultra stamp is one of those specials that gets the user killed most of the time, but when it works, that stamp gets like, a triple, so you have to constantly watch out for the stamps coming from behind. If brush gets behind you, it's basically guaranteed to get its special on retake.
Not to mention brush has pretty good gear freedom, so most brushes I see run some kind of spam build. Seriously, that thing can get 160p hammers without much gear investment, this is insane. Or splat bomb spam builds, hooray.
I'm rambling a bit here but my point is that I don't think brushes are inherently a problem main weapon wise (outside of clam blitz arguably), but they tend to play for spam more than any interesting distraction game, and if they just got less specials, or less snowbally ones (inkjet maybe?), they could be a lot more fun to fight.
I kind of wish they got 190/200p specials but dealt better damage to compensate, reward them for engaging with the main weapon a bit more.