I absolutely agree. Modern gearboxes are complex and many garages cannot deal with them. Most mechanics these days are trained to respond to fault codes.... and codes are not very specific, they are just an interpretation of a signal from a sensor. I agree, no "trained" mechanic really understands how to deal with a set of fault codes that cannot be converted into a real fault. It's not just cars... a few years ago I had a problem with a gas boiler in UK - the gas engineer said he couldn't diagnose the problem since he had been trained to interpret fault codes, and my boiler was ten (yes ten not a hundred) years old. His solution was to change the boiler for several thousand pounds. Obviously I said NO, and eventually fixed it myself with a £30 replacement exhaust fan.
You say you want to buy an automatic... there are not many better boxes out there. Torque-converter epicyclic boxes are becoming rare and beware of semi-auto boxes. Dual shaft autos are the best you can find. CVT boxes have their own issues. Electronics and software are the biggest contributors to problems and all boxes have that today.