It's not just because of hype that teams choose Mongo. The flexibility of a schemaless db is pretty helpful in a startup scenario, where the requirements drastically change all the time.

Yes, migrations work for RDBMS too, but with Mongo you only write migrations for data changes, not schema changes - which means a lot less migrations.

The option of having documents with embedded objects/lists makes it a pretty natural mapping to Domain Driven Design concepts, like aggregate roots + aggregates. One might even argue that while following DDD, it's preferable to handle most rules at the application layer and use the database simply as a performant, low-maintenance storage service. I know some folks here might view this approach as a sin, but it works pretty well too, especially for smaller teams without a dedicated DBA.

Maybe it's just me that haven't ran large enough systems to find the kind of issues with mongo that people always rant about, idk. Honest question: considering all these advantages above (from a developer's point of view), are there good reasons for choosing something like PostgreSQL over Mongo for typical business apps?