How do I get better at tricky wiring jobs?

You have earned real skill. Most of the work is yours now, and that took years. The gaps you notice on the odd layouts are not proof that you are behind. They are proof that you have grown enough to see where the hard parts are. Nobody masters everything at once. The tricky jobs teach differently than the routine ones, and you only meet them now and then. That is exactly why they still catch you. Not because you are slow, but because you have not had enough reps with them yet. Next time an unusual layout lands in front of you, slow down before the wire goes in. Sketch it out, check the code section you are unsure of, ask one tradesperson who has done it. One careful job at a time closes the gap. You are closer than you think.