This was a horrible experience you had indeed!
I have never had any experience
that bad, and I think most car dealerships do pretty well. Are they ripping me off? I don't know, because I know nothing at all about cars, but I suspect not, most of the time.
One experience I had was with a Nissan Sentra. I had one that would just stop accellerating when I stepped on the gas. They figure out it's the fuel pump, after a lot of testing, and fix it. Fine. Later I own another Nissan Sentra and I have the exact same symptoms. I tell them it's the fuel pump. They don't listen to me. (After all, it's obvious I know nothing about cars.) To make a long story short, after fooling around with other things that don't work, they figure out it's the fuel pump.
But most of the time things work out OK. I take my car in every 3000 miles for the oil change (I know I don't have to do it that often with new technology, but I do it anyway) and all other schedule maintenance. So far the vehicle has done well. (It's a Hyundai Sonata.)