I went from the 'real world' to academia. And yes, academia is full of a considerable amount of b*******, but so was my 'real world' working life, and I didn't value what I was doing enough to stick that part out; I am with academia - I've been teaching for five years, doing a p/t PhD for 2, and it is very hard, but I would not swap it for anything.
When I left school I took a practical, manufactring qualifiction (HND), and I felt exactlyy the same way about that as you did about your PhD - not wanting to be there, feeling my life was going down completley the wrong path, and feeling I was lost, and my talents wasted.
Yes, I love my PhD! It is very, very hard, but that is part of what I like about it: ask people who climb mount everest, or run marathons why they want to do that - that's my idea of hell, but I accept their joy in what they do - would you say they protest too much?
As for the usefulness of a PhD, that's very subjectve, and also impossible to discern in our situation, so we can't advise on that basis, it must come down to the indivdual student to make that judgement.
I'm really happy you've found the right path for you, and if you feel strongly about our advice being one sided, then maybe an alternative forum for students who are thinking of quitting would be a good idea, we're just providing some camaraderie, encouragement and support here: that's our agenda.