Understanding missing values in dataset
No generic approach in data handling. Role of DS is understanding data. As you know sometimes NULL value means something, you have to check all aproaches to handling data and I find out which is most suitable to yours data. 
Usually I marked missing value and resampling datasets. So I getting one dataset without missing values and another one with marked missing value.

Another techniques
https://www.kdnuggets.com/2017/06/7-techniques-handle-imbalanced-data.html

Best