If you feel that something does need to change, try your best to discuss those changes in terms of how they relate to the project’s goals, not what you like or don’t like. And if you feel that a point of disagreement is not mission-critical for achieving the project’s goals, consider picking your battles and moving past it altogether.
On Delegating
Matt LeMay

Very solid point here. Might be obvious but I think it’s worth mentioning that giving feedback in this way is most effective if the project owner adequately bought into the vision/goals. If they are are, then they’re less likely to view the critique as an attack