It’s just a fact that an ai will write and read faster than me. I can’t compete so getting ai to do that has freed up both time and mental capacity to actually think about the implementation details.

I'd like to think it comes down to my expertise, but I don't believe I did a lot of designing.

Sure, I've given a lot of inputs over the time, probably I've steered it to solutions that work.

Maybe it was also helpful that I set up a skill to use a different model to review the code for correctness, technical debt, and whether the location where the code is added is appropriate or warrants a new file or abstraction. I set this up long before subagents were widely used.