I do think there is such a thing as Standard English (Standard French, etc.), meaning the variety used in formal communication, but the standard is evolving rather than fixed. “Thou” was once the standard pronoun for the singular second person (except when addressing superiors) but was already obsolete by the eighteenth century and is now so misunderstood that people think it’s more formal than “you” rather than less (hence Darth Vader’s incorrect “What is thy bidding, my master?” to the emperor). Not only does standard language change, but it isn’t “better” than other regional or communal varieties. Every accent, dialect, etc. is interesting and legitimate in its own right.