I'm not sure I've ever heard of someone wanting to get rid of the *entire* brush class before. As for the gals and squeezer, I know some people think they are overtuned but that's more grounds for a nerf. And all those but Goo are kind of popular.
For better or worse all weapons seem to have at least some adherents but if we were going to get rid of any would think they should be the ones we don't see that often. The Nozzlenoses seem like good candidates, as does Goo. And Recyble Brella seems to have fallen off though it's kind of early to say for sure. Maybe Nova? Mini perhaps (I know this last one is very hot take but I honestly don't see it that often)? But other than those I feel like I see most of the various weapons pretty frequently.
Brushes are the only entire class that could be feasibly replaced. Most people agree that their design is, well, not good.
The Gals and Squeezer could be nerfed, hypothetically, but Squeezer specifically needs its semi-auto fire rate to be nerfed, and the Gals are inherently flawed in their power for accuracy trade-off. The weapons need reworks to become balanced.
I don't think removing weapons that aren't typically used is a good way to go about it.
The L-3 Nozzlenose suffers two outclassed kits, the H-3 Nozzlenose is one of the best weapons to have in the meta.
Goo Tuber is a more reasonable choice, but if Nintendo managed to fix the weapon it would undeniably be one of the most fun.
Recycle is bad, sure, but that's partly due to its kits, and a range or shield HP buff would drastically improve the weapon.
Nova... yeah that one's kind of a lost cause.
Mini has two bad kits and is easily compared to shooters, which hinders its popularity. When Mini is good, it's an awesome weapon.