How do I get better at installing complex electronic security systems?

You can install most systems now, and that is a solid foundation. The complex, electronic ones trip you because they are a genuine step up: more parts, more that can go wrong, more that is hidden inside the wiring and the programming. Struggling with them does not undo what you already know. It just marks the next stretch of the road you are climbing. The electronic systems reward a different habit than the simpler ones. With the basics you could often work by feel. With the complex ones you have to slow down, read the documentation, and understand how the pieces talk to each other before you start connecting them. The mistakes usually come from rushing into a system you have not fully mapped. Understanding first, wiring second, saves you the frustration of chasing a fault later. Take the next complex install and give yourself extra time on purpose to study it before you touch it: the manual, the diagram, how each component is meant to link up. Get comfortable with one system type fully before adding another. You are not missing some talent other installers were born with. You are on the ordinary path from good to expert, and it is walked one complicated system at a time.