Earlier quoted context omitted.
First of all, in numerous cases, the "national standard" (whatever that means) dialect is not the dialect spoken by the majority. Can you give an example of rules of "standard English" being easier to learn than some rule of non-standard English? Also note that English as far as I know doesn't even have an official codification of its rules and usage: https://www.wikiwand.com/en/List_of_language_regulators
I'll argue that Korean spoken in Seoul, South Korea is vastly different from one in Pyong Yang, North Korea, and arguably harder to learn because one can trace some of the phrasing to old way Korean was spoken which is a mix of Chinese-derived words with Korean. This is due to the language having been invented by King Sejong circa 400(?) years ago when most written language was Chinese in Korea. It's harder because y…
Anyway, we migrated from arguing about the claim "The rules of language are simple" to arguing that some language rules are simpler than other, which to me makes room for the claim that language is, generally speaking, complicated and its rules are complicated.