A voice actor must be able to accept and deal with constructive-criticism, as well as negative-criticism. If the talent’s voice instructor asks for a different ‘read’ of a script and the talent reads it in the exact same style as before, frustration can set in, before the voice over talent is even be close to doing a real gig.
Producers have no time as it is, and nor do they want to take the time to ‘coach’ a voice-artist through a reading. Listening and providing reaction to the criticism that a talent receives is almost as significant as being able to produce voices, characters, and read scripts well. It is also imperative to keep a keep an optimistic outlook when dealing with rejection, criticism, and hard times.