Marketing is not art. It is a science. However it is a behavioral science and therefore an imperfect science. Anything dealing with human behavior is imperfect at best. Yet it is still a science. You can predict and measure cause and effects.
Marketing is not art and it is not magic.
In order to be an effective marketer you must understand people and how to influence their behaviors.
Marketing is about guessing that if we do this, people will do that. The guessing part is important. The significant part is guessing how many people will do that.
What do you do? Predict – test – measure and adjust.