I believe his complaint isn't about not using MongoDB, but about storing JSON as strings in a database that supports actual JSON(B) data type. As you said your

I believe his complaint isn't about not using MongoDB, but about storing JSON as strings in a database that supports actual JSON(B) data type. As you said yourself, you migrated to PG JSONB columns, not to PG Text columns for storing JSON. So it seems to me that you agree with the author.