A GA aircraft is like a car (with wings.)
There is nothing to study in a car. It can go left and it can go right and there is an accelerator and a brake. And there is a KMH / or MPH gauge. One driving license hour and you fully “get it” and be able to drive (the rest is just learning all the traffic rules and more).
The same goes for any GA aircraft - just like cars all drive the same all GA aircraft fly and behave almost the same. If you can fly a Cessna 152 you can also hop into a Mooney Bravo and every other SEP and there will be no surprises.
GA aircraft can be modeled with a lot of realism and attention to detail, or less realism - but they can never be study-level.
The missing features in the “lesser ones” are more or less always the same: Circuit breaker board not functional, no simulated engine failures and some other details that would be functional or at least present in the real airplane are missing, like functional heating fan on / off (with fan sound) and other fine details.
That´s why it is almost impossible to be not satiesfied with any GA aircraft addon - because it is what it is, no tons of hidden features and programming in half a dozen MFD screens, no ten dozen systems and subsystems, complex heating complex cabine pressurization and more.
An airliner must be compared to a huge complex ship and the cockpit is more a bridge with tons of MFD screens and systems and hydraulics and fly by wire and turbine bleed air airconditioning and FMC programming and satellite-navigation and complex engine monitoring and more, but any GA airplane no matter how good looking it is and how well programmed and developed - will always be simple. Because GA is simple in real-life too, just like a car 
So when people write for example Carenado aircraft have not enough system depth and are just beautyful looking but shallow - I wonder what they expect from a GA airplane. Programming the analogue MPH gauge, studying 20 PDF sites with detailed information how to “handle” the analogue variometer, and discovering at least 20 hidden sub-systems and features in the analogue artificial horizon gauge?
A GA aircraft is what it is and a simulated private plane or a Cessna 172 cannot offer more features more programming and more complex systems than the real counterpart has just to become more complex challenging and entertaining
The only thing that can be added to GA planes is only complex engine management, engine wear, engine failures, oil change, spark plug fouling, engine overheating, and other engine-related stuff.