There are 3 traits I think every great marketer needs to have. They are courage, curiosity and hands-on experience.
A marketer in 2017 needs to have the courage to try something new, to be ok when an idea or campaign fails and not be afraid to champion an opposite point of view. They need to have the curiosity to ask why and dig into the data to see what happens. However, this curiosity also needs to extend externally and make them want to talk with customers and understand what makes them tick, what makes them buy and most of all what makes them happy.
A person can have some or all of the above but if they don’t have hands-on experience then it’s all for nothing. Being in the trenches and understanding how marketing fits into a company and how to use the tools to create a feedback loop for your work is key. Hands-on experience lets you understand why and not just what you’re doing. That lets anyone be more effective at their job and not just more efficient.