If you don't mind, I'd love to hear why you felt we were far from being ready for production.
Our main challenge has trading off ease of installation and use with the inevitable feature creep that causes the lots of moving parts and learning curve you find meh about Pentaho. You're right in that we've focused on making the most basic of sql queries (via our non-sql tool) usable by anyone in the company on their own vs essentially producing an analytics SDK like Pentaho/Jaspersoft.
On the language front, we made a conscious decision to optimize for ease of installation and low maintenance overhead. While I agree, it's made contributing less accessible, it's been amazing how porting has made Metabase more stable and easier to install. We run a bunch of instances for people, and our ops footprint has been silly small.