How to continually improve advertising across paid media platforms

In 2019, how can marketers be expected to keep up with the growth and sophistication of digital advertising? How can they overcome the challenge of needing to be an expert in specific platforms while also maintaining a good breadth of general digital knowledge (both of which are needed to drive continued brand growth)? 
Cross-channel learning
There are many differences between digital platforms; however, they generally follow similar logic across the board. At a very basic level, if someone