From their own blog: http://www.metabase.com/blog/Joins
"So rather than spending time constructing complicated queries with a bunch of joins, create SQL Views instead."
No thanks. While I can write manual queries to join... and even make SQL Views... try selling it to the non-developers in the company. The entire point of a BI tool is to eliminate myself as a bottleneck.
Perhaps things have changed by now, I don't know.
...
And to get it out of the way: the same applies for Airbnb's Superset. It's cool and has a lot of different chart types, but 1) really hard to install and 2) data exploration is still hard.
The point with 'insights' is that you can explore the data.
Take this view:
http://insights-demo.mariusandra.com/explorer?columns=Order....
(long URL instead of a shortlink as those are cleared when I reset the demo database)
With no coding time I got a view showing orders by date by country. Now if I click on the rightmost field ("count id"), I can drill deeper and see the orders by the day/country right there. I can use it to investigate anomalies in data.
Right now you must click the data in the column, but very soon it'll be possible to just click it on the graph as well.
This is the niche insights fills and why Metabase and Superset weren't good enough.