1. Doesn't this make business logic quite a mess because normal and standard abstractions are missing? Won't new coders make horrible solutions to "reinvent the wheel" problems?
2. It would be trivial to implement a key-val data structure that is persisted to disk in almost any nice modern language. And there are very good No-SQL key-val stores to choose from that are backed by very large and credible industries.
The Node.js drivers. Are you sure those are not mainly due to legacy integrations rather than "we really just wanted to use the MUMPS db" ?