Node and especially MongoDB make it a non-starter for me. I work with about 20 small businesses and agencies, they want something simple to setup and deploy and move around, like WordPress (and even that is too complicated for a lot of them). Smaller companies usually don't have IT expertise in-house (unless they are funded startups, and then their expertise is a 20 year old with Linux on their laptop). They and their agencies outsource back-end work, but with their budgets and constraints they can't invest in or take risks with complicated setups and technology that appeals only to programmers.

I know no one wants to hear it, especially on Hacker News, but PHP + MySQL rule in the small business/agency space, and for good reason: easy to deploy, easy to find add-ons and libraries, easy to manage, well-understood, low risk, lots of people who understand the tools.