Earlier quoted context omitted.
Given their start point (a product unfit for public consumption) that is the absolute minimum they need to do. I at least will never trust Mongo for anything but a toy project. There are so many better options out there, options whose technical capabilities are as good as Mongo's marketing.
In the same NoSql space as mongo db? I can't remember not even one that passed fully jepsen test. Can you post some links to the better NoSql options?
Depending on the exact requirements Postgres (in the right configuration) and Redis are better options.
I'd argue that for 90% of MongoDB users - the group whose requirements were met by MySQL/MyISAM - would be better served by Postgres or MySQL with a proper storage engine.