And half of all pilots still don't understand it.
The point is that they don't have to understand it - as long as they do not give full control to it & continue to fly the aircraft. Once you abdicate your responsibility as a pilot to fly the aircraft & give it to the automatics, you are starting down a very slippery slope.
Fully understanding the automatic systems on an aircraft is desirable & everyone should spend time on this throughout their career, but with the complexity of systems these days & the lack of currency with some of the more unique & subtle areas of automation, no one can know or remember everything. That is why you should never give full control to the automatics. You should always be 'flying' the aircraft. The Asiana pilots should have been keeping airspeed & thrust indications in their scan, regardless of whether or not they thought the A/T was engaged & would control speed. If they had done that, the accident probably wouldn't have occurred. The Turkish B737 & the Colgan Dash-8 accidents also come to mind.
Attitude, altitude, airspeed & thrust need to be monitored at all times, regardless of whether or not the automatics are engaged. This is basic aviation as far as I'm concerned.