Adjective order in English is basically that most essential qualities of the object go closest to the head. There are lists out there that try to break this down into categories of adjective ("opinion-size-age-shape-colour-origin-material-purpose"), and to some extent the anglo intuitions on which sorts of properties are more or less essential are not trivial, but it's not as arbitrary as people want to make it out to be.

This. People act like it's a hyper-complicated rule that English speakers magically infer, when in reality, a) other languages do it, and b) it's a much simpler rule (that you've given) which someone overcomplicated.

As a counterexample (in line with your explanation), consider someone snarking on the WallStreetBets forum: "Come on, guys, this is supposed to be Wall Street bets, not Wall Street prudent hedges!" Adjective order changes because the intended significance changes. (Normally it would be "prudent Wall Street hedges".)

Side note: please don't nitpick about whether "Wall Street" is functionally an adjective here. The same thing would happen if the forum had been named "FinancialBets".

Isn't this a bad example? There's only one adjective in "prudent hedges." Changing which noun "prudent" acts on isn't a matter of adjective order.

(I suppose Wall Street is a proper adjective, like "New York pizza," but you said no nitpicking)

People "overcomplicate" the rule because they find counterexamples to the simple rule.

It's a fool's errand because the way human language works is that people happily accept odd exceptions by rote memory. So the rule simply says that there exist these exceptions. Also, there is something called euphony: speakers find utterances questionable if they are not in some canonical form they are used to hearing. For instance "black & white" is preferred over "white & black".

The rules boil down to "what people are used to hearing, regardless of the underlying grammar offering other possibilities".