Compared to being the kind of person who reads use-package like JSON and treats it like a declaration language, you will be light years ahead at configuration if you just know lists, quoting, alists, plists, and writing functions.
Hey, use-package user here. I switched from my half-baked NIH init framework with a bunch of functions and other stuff you're talking about, and never looked back.
My 1670kLoC config doesn't contain any definitions and mostly declarative. If I need to defun something (so, there's no package with similar functionality) - there's definitely time to start another package. I don't even need to publish it on MELPA, since installation from git sources hasn't been an issue since Quelpa appeared (like 10 years ago).
Users who don't go at least that far will be constantly shooting themselves in the foot and spending much more time with minor, novice level bugs that are completely obvious.
Debugging use-package forms is very easy if you know about macro expansion.
just add two spaces at the beginning the search string