Before legal papers are signed. As a manager, I cannot expect my artist to negotiate a contract, chastise an agent or sign off on a publishing agreement. Likewise, they do not expect me to work on their song structure or help stage their live shows. The issues are complicated but the answers are simple. Inasmuch as I work for the band, I need to help them in whatever ways I can.
Many bands are open to managerial objectivity on creative matters.
Some are abhored by the very thought. A simple, courteous discussion with the artist will resolve the situation. The trick here is to let the artist be the artist. Pointing out that some thing is bad without giving options and suggestions on how to make it better, is not constructive criticism. So, to conclude, it's not about authority or power or being in charge.