The result is the chaos of the present day.
That said, would anyone have been interested in a totally new encoding? For European languages which use mostly the same 26 latin characters with occasional diacritics and accents, UTF-8-with-incompatible-consumer degrades into occasional unreadable characters. But if your out-of-date browser or application gave you a "cannot decode this encoding" error, that might have caused a whole lot of pain during that transition. Not to mention that some of the same issues with OS/filesystem/language library interaction would probably remain.