Not that dumb considering how often common dialect changes when society changes. Hell, a hundred years ago the N word was very common use. five hundred years ago people spoke with thou and thine and shit.
When words are no longer commonplace nor socially acceptable, that’s a change that society has changed. People don’t set out on inventing words that cannot be used, words no longer get used as a sign of changing times. The reverse is true too. With new generations come with new words.