Maybe this will help your perspective. I fly for a living in machines with very complex systems and avionics. My employer (and the FAA, and the public) REQUIRE that I know these systems inside and out. We train every nine months, fly at least 75 hours a month, and many of us have a wealth of knowledge and previous experience with the same or similar systems/avionics suites.
Having said that, there are still many things about my work plane I don't know perfectly. Almost more that I don't know than do. There are always the tricks and tips, or little known gee whiz facts that only some will know or ever use. We still get from A to B safely, and pass our exams and sims with no issues.
So maybe take the advice being tossed out here: Learn the basics, be able to know where to look for critical information (that probably amounts to altitude, airspeed, and engine rpm/cht/oil pressure etc). Then work your way into more as you go along. I think you'll find that while flying, you will come across a need, notice a new capability, or want to modify a parameter. Then you'll come home and read up, then go out and give it a try. Little by little you'll add to your knowledge bank, soon being able to do everything you need to do. Probably not everything in the book, but everything you need.
It's not really that hard, but if you're coming from steam gauges it can be intimidating. Start out small, you'll do fine!
Fly well