If you're ok pulling the data out of Postgres into memory locally and mostly care about manipulation and beautiful dataviz, then look at Tableau.
If you're mostly interested in more data sciency/ML stuff, then Shiny or something else that's R-based is a good option.
If you're interested in being able to embed your business logic into the tool so that non-SQL folks can build their own queries and everybody's relying on the same data definitions, that's where Looker (disclosure: where I work) excels.
A side note: I love that Caravel is written in Python. Metabase switched from Python to Clojure, and I personally believe that to be a barrier to entry for contributing. I've started down the Clojure path a number of times only to stop because I see it as something which would be difficult to impose on my team...Lisp is just so different from what most enterprisey development teams are used to. Python, on the other hand, is easier to justify. I've found things I wanted to help fix in Metabase, but having to learn idiomatic Clojure just to submit a patch is a turn-off.
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.
If I recall, it was difficult to understand how to properly format the results of a raw sql query to graph. Also, even once properly graphing, saving the graph to a dashboard wouldn't scale properly and would render in a very jumbled manner. Perhaps these issues have been fixed with newer versions....I'll give it another look next week.
Disclaimer: I am one of the founders.
Our site is here: https://www.periscopedata.com/ and if you have any questions, shoot me an email at jon@periscopedata.com.