Totally fair. I think a lot of the things we used to do in the name of efficiency has been completely lost in the progress of time. Largely from the emergence and refinement of JIT compilers, I think?

That is, a lot of why you would go with macros in the past was to avoid the expense of function calls. Right? We have so far left the world of caring about function call overhead for most projects, that it is hard to really comprehend.

Coroutines still strike me as a hard one to really grok. I remember reading them in Knuth's work and originally thinking it was a fancy way of saying what we came to call functions and methods. I think without defining threads first, defining a coroutine is really hard to nail down. And too many of us take understanding of threads as a given. Despite many of us (myself not immune) having a bad understanding of threads.