(Mind I mean the discussion is misguided, not you)

The problem is that relational model is a one solution to certain problem of when you want to pay the price of enforcing the model of your data. Relational database is when you pay all the cost upfront.

With MongoDB I have other options.

It does not mean they are necessarily better options. But some of them are better in some situations, for example when rapid prototyping. Or when you need to preserve data in different formats as the application evolves.

Personally, if you can, you probably should model your data upfront. But it is good to have other options, sometimes.

In other words that you don't see a use case for JSON columns because you don't think it's good DB design.

I know I have used them after decades of RDBMS work, and it feels like I'm "cheating" a bit. But they really do make sense for some use cases that can be harder to achieve with traditionally normalized RDBMS alone. For instance, for configuration options or scenarios where different objects may have a few different attributes, but are largely the same.

If you've ever used an entity-attribute-value data model or otherwise ended up with table proliferation or a bunch of nullable columns to accommodate the latter use case, you might appreciate the simplification JSON columns offer.

I have a hard time justifying a document database in 2024 when I have 2024 Postgres; I don't know how large the window is where MongoDB will do something Postgres won't, but I know my systems are not in that window. (Assuming it even exists, which I wouldn't be surprised it doesn't, but for the sake of argument I will assume it does.) But a decade ago that would be a much harder decision if I truly had a document-based use case.

You're right, 9.4/9.5 were when JSONB was introduced and expanded (release 2013/2014).

That said, it's a big decision to go with two very very different technologies (relational vs Document store) just for a column type, storing JSON must have been a pretty major product feature?