I think the rule derives from a lot of strawmen arguments that run “I like to play games concentrating on $THE_GREATEST_THING. D&D doesn’t do $THE_GREATEST_THING. Therefore D&D is broken.” The rule says “Respect what the game does, understand how and why it does it, understand how that affects other things, and then you are ready to change it or change something else to get the effect you want.”
Note, this rule is just as valid for any RPG. If you are committed to playing Mage: the Ascension but something about the game is sticking in your craw remember “Mage is always right.” Go through the process above before you just change things randomly.
This is the same difference between patch rules and rules from first principles that Ron Edwards discussing in Fantasy Heartbreakers.
For those having trouble what is wrong with just saying “D&D is broken” may I present We Tried Baseball and It Didn’t Work