Thank god you're not responsible for the design of complex, life-critical systems, like those commonly found on passenger jets, in nuclear power plants, in high-speed rail systems, etc. All of those systems incorporate fail-safe measures so that if something were to go wrong (like an operator losing control) the system would fallback on a safe state.
Sure, in an ideal world, every operator of a life-critical system would have total understanding of that system, know the value of every system setting at all times, never forget, never be tired, and have an IQ of 200. In the real world, operators are often overworked, susceptible to distractions, minimally qualified, and sometimes under-trained or even improperly trained. Even the most experienced and well-trained veteran airline pilots can lose focus and make deadly mistakes (which is why Cockpit Resource Management has been a major area of research in aviation psychology). You can base your system design on ideal conditions, or you can base it off of real-world conditions; either way, it's going to be operating in the later.
You also seem to be missing the main purpose of mechanization and automation, which is to simplify a task or make it easier to perform. When you buy a cappuccino machine, you don't want to understand the details of how it operates or be asked for input every step of the process to make a cup of coffee. Eliminating/minimizing the human factor in a particular process is another major advantage of automation. It provides more consistent results and helps to minimize human error. All of this helps to reduce the learning curve and skill level required to perform a task, which confers economic benefits. However, not every well-designed system can necessarily be operated by unskilled personnel—nor would you want a high school drop out to be operating most life-critical systems. Nonetheless, you still want mechanization/automation to simplify the task in these cases. That's because some tasks are so inherently complex and mentally demanding that, without automation, it simply can't be performed.
Flying a passenger jet is a perfect example of this. Even with all the sophisticated automation (including autopilot) on a modern airliner, it still takes a full cockpit crew (not to mention support personnel on the ground) to safely fly & land the plane. With all of the complex duties that airline pilots need to perform simultaneously, they don't have the time to monitor the status of every system component or manually adjust every actuator on the plane to control its flight surfaces. It may take 50 different mechanical actions to retract the landing gear on a plane, but why clutter the cockpit interface with 50 items when a single switch or button will do? Likewise, doctors and nurses are already required to undergo extensive medical training; they don't need to have to learn how to mechanically calibrate a CO2 laser or calculate the spectrum of an X-ray machine based on the anode material of its emitter and the voltage passed through it. Medical personnel should mainly be trained in medicine and only need to learn how to operate a particular medical device, not how to troubleshoot it or read its blueprints.
A simple and streamlined interface is much less distracting and more intuitive than a field of buttons and dials for a thousand different minute settings and system readings. Even with the utmost simplification, most industrial machinery and complex systems are still overwhelmingly difficult to operate by an untrained person. It's never just a single "magic button" for the operator to press. A nuclear power plant might take hundreds of different readings from multiple sensors and summarize it with a single status message or indicator light on a controller's console, but that message/light would likely be sitting next to a dozen other status indicators that each take hundreds of other readings. And although a complex process like lowering the reactor temperature might be simplified down to a single "magic button," the controller interface would probably be comprised of several dozen such buttons. And it still takes a skilled operator to know when to trigger which actions, how to read/interpret different sets of indicator lights, various safety protocols, etc.
Simplicity is not the problem. And even if it were, ditching the benefits of automation while ignoring human fallibility are certainly not the solution.