It's true that professors rely on grad students/postdocs to do work. And, at least in my experience, advisors are actually pretty good about giving students credit for their work -- having successful students reflects well on the advisor. But a student is even more dependent on their advisor than vice versa. It's not like undergrad where the main thing that matters to your future employment is to collect the diploma, because for most fields the main reason to get a PhD is to continue in academia, and academia right now is an extreme employer's market. The things you need to leave grad school with are 1) impressive recommendation letters, like "best student in N years, reminiscent of <mid-career hotshot> at that age", and 2) (lots of) refereed publications. If you manage that, the diploma should be automatic.

Yes, you can push back against advisors who require 12 hrs a day in lab. But if that means you take longer to produce work, your letters might be just good instead of positively glowing, which might mean you fail to launch in academia. Several hundred other people will apply for each tenure track job you apply to; those with "just good" letters tend to get crowded out. The tenured advisor might have a bruised ego because their publication rate has slowed, or be more frazzled because they have to save money and write more proposals, but at least they still have a job.

Also, PIs themselves generally work a lot as well (often the ones insisting on lots of hours from their students think, rightly or wrongly but based on their own experience, that that's the only way to succeed....). I agree academia is broken, but think it's at a deep structural level, and more complicated than schools exploiting students and hanging them out to dry.