"A little OTT. How do people learn to maintain their house or learn to hack improvements? Should we all have your expertise? Perhaps you think paying a qualified installer would be better?"
Start with low voltage instead of high voltage. Learn how it works. When you know enough that you want to move to high volt, don't start with improv -start with repairing outlets, replacing lights, etc. Things that have good directions, are not made up by you, and you can read and study. Read the relevant electrical code portions when you do it, understand why you have to do things the way it tells you to.
As you get better at it, and understand more and more, sure, branch out into your own stuff. But not until you understand it and can be safe.
Messing with mains when you have no idea what you are doing isn't just dangerous to you. It's dangerous to people around you, to future homeowners, to houses around you, etc.
Mistakes in the field are not meant to be part of the learning process, anymore than they would be in any other hazardous-to-life situation. Sure, they happen, and risks exist, but working on mains and high volt panels in any sane place is learned while you have you have someone overseeing your work and stopping you before the mistake is dangerous. People stop and ask whether what they are about to do is the right thing before they do it, not try it and see if it works.
Otherwise, it's not just money, it's your life, or someone else's life.
As for learning having risks and mistakes sometimes being expensive - sure. But having never dove in a pool, would you think it's a good plan to try to do a triple backflip off a ten meter high dive?
After all, any way you learn to dive runs risks, and making mistakes is often an important part of learning (and can be expensive).
You would instead hopefully start small, work your way up, understand things, and be appropriately fearful of things you should be fearful of.
Beyond that - I don't know why people are so tolerant of this kind of thinking with high voltage stuff.
People seem totally intolerant of it when it comes to natural gas lines, for example. Nobody is out there saying "well you know i just started fucking around with my gas line, added some tees and some relays to control some valves. Sometimes it smells funny but who knows. I wrapped some more tape around it and it seems fine most of the time".
Messing with mains is much more dangerous.
Electrical codes are written in blood, the same as all others.
If you want to learn to do home fixing, you learn to be safe first, you start small, and you don't improvise until you can be safe.
Like safety everywhere, it's about understanding, discipline, and process. You can't shortcut it.