And in turn put the schema (actually multiple versions of it) in your application making it more complex.

Since Relational Algebra was invented in 1970 we were unable to find a better representation of a relational data, there were many attempts but so far they failed (except for very specialized uses). So I'm inclined to believe it's here to stay.

JSON is basically just step backwards back to the XML Database[1] and Object Oriented Database[2]. It starts falling apart as soon as your data becomes more complex (you have relations, or need to query it by something else than primary key). Having said that, I'm glad that relational databases added support to it, it perhaps might be useful in early stages when things are in flux.

[1] https://en.wikipedia.org/wiki/XML_database

[2] https://en.wikipedia.org/wiki/Database_model#Object-oriented...