Building a quality product takes time, and often times a lot longer than you think it will take. Lots of things get in the way, and with a product like this, education is a huge part of the adoption cycle. At 500k/year, they are poised to have healthy growth until they reach that point. Might not happen on your timeline, but at least they are still chugging.
Hell there's a company in my area (sadly I worked there years ago) who literally manages 200+ local businesses sites and they're all powered by WordPress. I'd say 1 or 2 of them are actually blog having sites. The rest are just "I want to be able to edit this section of content myself" sites.
WordPress makes it insanely easy to build a site for a client or even anyone who's vaguely familiar with web development.
Go get a cheap shared hosting account, click that 1 click WP install button, login to your new site, search for a theme you like, install it in a click, make a few minor tweaks, find some plugins that do stuff you like, install them in a click. Done.
Until people realize this, there's no "taking on WordPress".
We have npm already to cover the plugins functionality and on the front end it's a framework-a-palooza with libraries and themes popping every other hour.
So, it can be done and I believe it can be easier and simpler whether for the end user or the developer as developing for WP is not really a walk in the park and there's a lot of gotchas and magic involved in this daunting process.
"Why would I recreate this in NodeJS where nobody uses it, when I can just use WordPress?"