Might I suggest you actually use mongo on a project before engaging further on the topic. It clearly has had a lot more thought put into it in the context of json documents.
If postgres works great for your use cases, great, go be happy with the tool.
Your response seems to betray a certain ignorance of mongo. Don't you realize that mongo has indexes?
For handling documents, this blog post covers the topic in some depth.
https://jimb-cc.medium.com/postgres-jsonb-meets-mongodb-part...
Might I suggest you actually use mongo on a project before engaging further on the topic. It clearly has had a lot more thought put into it in the context of json documents.
If postgres works great for your use cases, great, go be happy with the tool.