Compared to a product like Oracle, transactions on MongoDB are very new, very niche functionality. Even MongoDB consultants do openly suggest not to use it.
MongoDB is really meant to store and retrieve documents. That's where the majority read/write concern guarantees come from.
As long as you are storing and retrieving documents you are pretty safe functionality.
Your article presents the situation as if MongoDB did not work correctly at all. That is simply not true, the most you can say is that a single (niche) feature doesn't work.
Have you ever tried distributed transactions with relational databases? Everybody knows these exist but nobody with sound mind would ever architect their application to rely on it.
Any person with a bit of experience will understand that things don't come free and some things are just too good to be true. MongoDB marketing may be a bit trigger happy with their advertisements but it does not mean the product is unusable, they just probably promised bit too much.