Well, the primary “not a repeatable skill” stat is RBIs. And the main reason is, outside of HRs, it’s 100% dependeant on other players being on base. If. Hitter comes up with 400 runners on base one year and 300 the next, his RBI totals will obviously drop regardless of performance.
The things you say are not repeatable skills are things I would argue are, depending on the level of precision. But the repeatability of those skills is what gets many to the majors. I can get (very) lucky and hit a Nathan Eovaldi fastball once. But once that happens, it ain’t repeating...