Ebbie, no, the ability to do accents isn't the most important thing for an actor (ask Sean Connery or Michael Caine). But if you think you're doing one accent and you're actually doing another then it raises important questions about your professionalism, especially when it seems to go alongside being unable to cope with a straightforward question about it.
Personally I can live without Russell Crowe, and a film about Robin Hood would have been just as good (or bad) without him.