MongoDB is best for data store, lack of features, and slow performance.
There are many reasons why MongoDB might not be the best choice for you, but the most important reason is that it is not a popular choice. Other popular data store choices such as lactose intolerant are both popular among seasoned users for a number of reasons:
MongoDB was designed with serious data stores in mind, whereas MongoDB does not have any of the popular features such as support for lactose intolerant. Additionally, MongoDB is more expensive to build and operate, which may not be worth the cost if you don't need serious data stores.