Hello roulis;
We used to have the DC8's systems memorized. We had to be able to draw the terminal and airport charts of Chicago and New York as part of the route check-out on these terminals. We also had to know Morse Code at 5wpm and draw models of frontal weather from the forecasts and SA's, (now METARS), prior to graduating from our initial airline groundschool of two months.
Gradually, as more complex aircraft entered service, the "Need-to-Know" concept took "knowing"'s place. It wasn't possible to know all there was to know about the airplane one flew. So training priorites had to be adjusted and everyone was making it up as they went, particularly when the Airbus was introduced. Even reading the books didn't fulfill the need to know however, because they were very thin on information. So, (personally) I went to the AMMs to learn, (as I'm sure others did).
Most of the time it worked well. When things are going well, flying is easy, but that's not the reason we're there, (and it's the reason why there will never be a pilotless commercial air transport system that replaces the scale of aviation services we have today).
Today, much of this knowledge is handled by software. Also, we now have an entire generation of pilots in the cockpit who grew up interacting with computers and know them intuitively.
The difficulty arises when the assumptions are made that computers "are" airplanes and "know" aerodynamics, etc, etc.
I think you are expressing some important notions regarding competency, knowledge, capacity and their polar opposites. The mistakes are made by both management and the pilot group, the first in assuming that because the airplanes they purchase have sophisticated software autoflight systems which reduce the need for training and competence, and the second group in assuming a relaxed and cold-soup-accepting stance when it comes to automation and both the requirements and the inviolable rules of aviation regarding personal knowledge, ability, skill and competency. That is the essence that makes a pilot a "professional" vice merely a journeyman in the cockpit.
It is up to both groups to get their act together. By and large, from what I see at conferences and in those associations I continue to maintain with aviation after retirement, that is happening. But we are indeed in a major transition phase between analog and digital flight even as the fatal accident rate remains remarkably, enviously low.