Actually, regionalisms are absolutely valid. People rarely say "Tis or “Tisn’t” any more. People don’t say “Od’s Bodkin”. But would you say that Shakespeare’s plays aren’t acceptable? Good luck in imposing your personal viewpoint on the uncaring universe.
Pronounce things differently from the people around you, and it marks you as an outsider and impedes social bonding and communication. There is NO “perfect” use of language. Language in general is a TOOL, Not a mandatory STANDARD, not an absolute fixed object. If you get your meaning across effectively, you have used language correctly. “Everyone else does it”… yes, exactly. You could use Esperanto perfectly according to the published grammar book. If nobody else uses Esperanto, you have failed to communicate. If you use your “perfect” Esperanto and some group of people have developed a regional pronunciation and grammatical variation through daily usage and reliance upon the language as a primary means of communication, then you would be “wrong” to insist on your way. If you could magically communicate with a 1st century Roman Legionnaire, I can guarantee that even perfect grammar school Latin of recent centuries would not effectively communicate with him, no matter how precise your declensions.
Language is ALWAYS a mutually negotiated protocol. Across generations, across regions, across specific occupations, the meaning of specific words, their pronunciation, it all is negotiable and changes from time to time in both specific and general usage. Get over it.