I quit recently after 5 years. I don't think I regret it - the improvement in my mental health has been dramatic. I found it difficult to trust any of the advice I was getting from supervisors etc. because our interests weren't aligned.

I can say that I'm significantly more highly skilled than when I started though. Knowing that I didn't want to stay in academia, I spent a lot of time working on my transferable skills (i.e. tech).