Art Directors who don't respect you will certainly love you to bits -- by which I mean hassle you slightly less -- if you can pluck out their thoughts and draw them in a style they think is close to what they're thinking of.
In the real world, different artists have different styles and it's an insult to expect any two artists to draw in the same style. Asking about a unique style as opposed to just aping someone else's style for one's own storytelling and one's own unique, independent project, there's only one answer: cultivate one's own unique style.
If you want to be an animator and draw the same thing a million times and try to imitate the other animators' styles, sure. Go for it. If you want to be part of a machine of any sort, that's your choice, @keac . But that's not what I think you were asking in the first place.
If, however, you want to cultivate a distinctive style that is identifiable as your own and not have people mistake you for someone else, work on your own unique style. As I pointed out myself, do drawing from life to develop your abilities and strengthen the fundamental foundation of your work. But don't imitate others in developing your style. I do agree, try to do things that others do...but do it in your own way and realize it in your own style. Don't just try to make it look like someone else's, because that's really not going to happen in most cases.
I've imitated other artists in learning exercises, stared for hours at other artists' pieces, and that taught me lines to value in my own work and values to imitate in my own work. There is, as @dojo said, nothing wrong with imitating styles if you choose to do so. But feeling like you have to do it to fit in, or even to be well-regarded...is just rubbish and nonsense. Don't do it to fit in, don't do it because you think those styles are "better" -- they're not. They're just different. There is no such thing in art as objective good or bad. There is technical merit and no end of other qualifications, but no absolute "good" or "bad". Art is an expression of personal perspective. When it is a successful expression, that's when it tends to feel like its best.
I've been at this for most of my life and I know what I'm talking about when I say that a unique style will serve you far better than a chameleon ability. Adaptability, flexibility, these are important; however, if you cultivate strong fundamentals and a strong foundation to go with your unique personal style, that will serve you far, far better than the learned ability to ape what other people are going to do better than you no matter what.