@blinks something like a design bible, a glossary of common problems and complexities, with references to common design tropes and implementations that attempt to tackle them (and ideally with some commentary on how/why/if they succeed) would be such a valuable resource.
I'd love to see something like that condensed down into something quick and easy to digest like https://yourbias.is/
@darkliquid That's exactly the idea; in the Discord we call it The Book.
@garykac is working on a bit of this focused on complexity as it affects "time to first move" in tabletop, though we're talking about a bunch of related subjects in there, too.
I find that loads of things come up again and again when we talk to new and inexperienced designers. Just learning a new concept can help you look at your game differently.