I'm lucky enough that I understand most of the tricky parts of Rust other people stumble on. I guess it comes from an academic background and a decent intuition.
But the type-level magic that frunk accomplishes, I don't think I'll ever fully understand. There got some great blog posts about type-level recursion and the black arts powering frunk. I love reading these; it's a fun walk through (ab)using the type system to do awesome things.
But I don't think I'll ever be writing something as involved as frunk, diesel, or libp2p. I've written some absurdly generic code on a smaller scale, but the scale at which the above crates operate is an order of magnitude beyond where I can struggle though compiler errors on my own power.
Sure, I can probably wrap my head around it after the fact, but writing it is another story. (Let alone extending it in useful ways for writing generic APIs.)
I'll be sticking to my needlessly involved (proc) macros over needlessly involved trait impls, for the time being.
I thought up a clever qotw bait one liner to stick in here that prompted me to actually write it then forgot it while writing the post in favor of being genuine... whoops