Isn't that example pretty reductive, in that you have a directly-measurable output? I mean, the joint is either 45° (well, 90°) or it's not. Zoom out a bit, and the skill-set becomes much less definable: are my cabinets good - for some intersection of well-proportioned, elegantly-finished, and fit for purpose, with well-chosen wood and appropriate hardware.

Mind you, I don't think the process of improvement in those dimensions is fundamentally different, just much less direct and not easily (or perhaps even at all) articulable.