Your mnemonic seems good for its purpose.
You should know that the rule in question does have exceptions, and this is actually a shockingly complicated and controversial subject:
https://english.stackexchange.com/questions/1155/what-is-the-rule-for-adjective-order
As Jasper noted, most native English speakers are not taught this rule but instead absorb what sounds natural through osmosis. While the rule might be helpful for writing, I don't think you'll ever be able to apply it at conversation speed, and you should probably supplement it with repetitive practice of common multi-adjective phrases.
The 'standard' order of adjectives is the Royal order of adjectives, memorised as DOSSACOM Q. This is standard across all varieties of English, and even non-English languages that allow prenominal adjectives.
Whether English users get it wrong is more difficult to answer. Underlying the royal order of adjectives is another ordering of determiner > specification > description > categorisation > noun. This is fairly solid, but within the three zones of specification, description, and categorisation the order is more of a tendency or preference than a rule.
This is because underlying that is the principle that the more concrete, intrinsic, or "nouny" an adjective is, the closer to the noun it goes. For example, if we compare the large round coin with the large round table, 'round' is very concrete. They are either round or they are not - there is not much to argue about and 'round' has the same meaning for both, so it is placed close to the noun. 'Large', however, is relative. A large coin is much smaller than a large table, and a table the size of a large coin would be considered tiny, so 'large' is placed far to the left of the noun.
There are limits to this. Size, length, and height are equally "nouny", concrete, and intrinsic, yet they appear in precisely that order, suggesting that it is mere convention. On top of this, deciding how "nouny", concrete, or intrinsic an adjective is, is quite subjective. This makes the whole notion of 'wrong' a bit cloudy, at least within the previously mentioned zones.
Best Answer
It's worth copying in a line quoted by the top answer when this was asked about on ELU...
I'd also have to say that "opinion" is a very slippery (not to say subjective) word category. If beautiful is an "opinion" word then the same must surely be true of ugly. But apparently the rules are different...
In short, what OP is missing is that "order of adjectives" is a complex issue. But note that doesn't mean "different grammars" disagree about what's correct (these days, "correct" just means "most common").
The reality is actual native speakers tend to be consistent about the order they prefer for any given set of adjectives, but grammarians/linguists struggle to describe/define those preferences in a way that would enable non-native speakers to predict what form the natives will choose (i.e. - formal "rules").
But OP should also note that not all sets of adjectives will be consistently sequenced the same way by all native speakers (a point I hope the above two charts encapsulate, as well as showing change over time).
As a native speaker, I know instinctively which of these sequences is "normal", but the rules don't help...
In short, it's probably worth learners taking note of the basic sequence...
...but you've only got to look at the comments against the ELU question and answers to see that it doesn't work in every case (and things get particularly imprecise around category #2 above).