Idk about hype, but for node.js virtually every tutorial uses it. I think the stereotype is that postgres locks you into a data model but your needs vary drastically. I suspect mongo is harder to retool the schema than it is widely claimed, while pg/msql is slightly easier than is often claimed.

I doubt they meet in the middle, but both have great use cases. scaffolding out a quick isomorphic js app is great for mongodb for example. pg is faster and more robust.

its just tech, depends what you are optimizing for