I think you're looking at it the wrong way, the actual flight controls are pretty rudimentary and simple to understand. The dials represent information and tools available to the pilot should they need them. They're all pretty simple taken in isolation, and they usually have configurable warning states, so you don't need to watch them like a hawk.

Also, you can halve the count in most cockpits, as they'll be redundancy duplicates or co-pilot duplicates. Cognitive load during flight is pretty low, too, so plenty of time to keep an eye on things. Landings and take offs are prepared for with plenty of time ahead (at least they should be) so again, plenty of time to check and configure.

Over time, you get used to where all the gauge needles should be and it becomes easy to notice if something is out of place. The AAA gauges, Attitude, Altitude, Airspeed are the most important, and also the ones that change a lot. Something like EGT or the voltmeter is just for diagnosing error conditions. A warning light will turn on if one of these values gets out of wack.

Numeric displays require a lot more conscious effort to read a number, decode it , decide if it is an acceptable value. This is why the steam gauge style remains popular, even if it is a digital render now.