While I will not argue about the complexity of the modern aircraft, your argument does not explain why being more complex, there is now only 2 instead of 4 in the cockpit. It is not so much the complexity insomuch as the simplicity of flying a modern aircraft, thus removing the need of a flight engineer and a navigator.
As for the grandmother stories, of course during the flight, their eyes are always glancing on the instruments and out of the windows and making small adjustments pn the controls as it is on autopilot. Once in a while they might make some flight checks, and record some information. Why I know is because I flew a few times on the jumpseat in the cockpit.
Why 2 and not 4? Because of cost cutting measures. The computer alongst with technology such as the GPS and other ground based instruments help enable that flying a plane is more precise.
It's too small a space to try and explain the complexity of what it takes to fly the aircraft. Where pilots previously were stick-and-rudder inputs, whilst the engineer used to handle technical faults, pilots are now expected to fulfill that role. The population being more educated helps in that aspect.
I do agree that if all goes well, the task seems easy. But there's more to it than just that. Even as a stock trader looks at the stock market and does not trade, not trading in itself is a decision. And that decision requires knowledge and skill to work.