No. And for the record, come on, now.
This question was posed to me a few weeks ago by a fretful student who was about to travel to London for an ESL summer learning program. Her friend, she informed me, had trouble being understood by Londoners, and she was afraid of a similar fate.
The first thing that popped into my mind was that her friend's English must be on the rotten side. I didn't say this out loud. The next thing that occurred to me was that London was one of the most diverse cities in the world; native English-speaking Londoners have actually become the minority in this hub of multiculturalism. This, I did say out loud, explaining that anyone who lives in London has to develop a pretty good ear for accented English if they want to interact with others in the city.
The student was unconvinced, and tried to compromise. "Well, instead of can [kan], could you just start saying can [kon]?"
No! I wouldn't! But I was more amused than frustrated. English language learners often hold accent expectations that puzzle us native speakers. In East Asian ESL teaching circles, I've heard stories of language schools so fixated on clear, "proper" accents that they won't even read the CVs of teachers from Scotland or the American south. An English friend of mine was asked by her Korean employer to teach in an American accent.
In Thailand, my local friends held the view that, as non-native English speakers, British accents were more desirable. "British people just sound more intelligent," they would say, echoing a feeling I once held myself before spending extensive time with British holidaygoers in Thailand.
A coworker of mine recently reported that her students were puzzled by Canadian English after reading an article comparing North American cultures. "Could I learn proper English there," they asked her, "even if the people say eh after each sentence?" To them, this eh was a grammatical nightmare; an article without a noun, hanging erroneously at the sentence's end.
Now that I think about it, only one accent-related complaint might be below par, teaching-wise...