I can agree that some studios are unethical in the cut that they take and their treatment of models, and that if the girls are camming through a studio on the major sites her full situation probably won't be anything near transparent to members.
On the other hand, some girls would not otherwise have the opportunity or resources to cam if it wasn't for studios. I'm referring here mainly to physical studios (those that only provide "advertising and support" don't deserve their cut for the most part, in my experience, and are often predatory). A girl's living space might not be suitable for a whole list of reasons (not enough room, lives with parents or roommates, can't yet afford equipment...) For those who are getting tangible benefits, I think it's fair for a studio to take a cut. After all, girls who work from their own space are paying extra rent for a cam room, premiums for faster internet, etc. that in the case of a physical studio are theoretically what's provided for her with that extra percentage she gives up.
So that's a trickier situation to suss out. Studio girls in all sorts of differing circumstances, good and bad, may not be willing to talk about it, so it's up to your own discretion. I don't feel great about suggesting for members to avoid studio models altogether. Not even to avoid all eastern European studios, though the only studio girls I've communicated with much one to one about it have been from North America. I think it's best to use a little intuition. But yeah, obviously avoid rooms where it's clear, say, that somebody else is typing for the girl or where the she's frequently falling asleep on cam. A studio is usually pretty easy to spot. A shady studio has its own set of red flags if you pay attention for a while.