Riak convinced me that any language pretending that it could magically create better products was full of shit.

Riak is not great. It performs well, but doesn't scale well. It has tons of operational overhead, a lot of bugs (and it didn't help that a slowly disintegrating company left less time to fix those bugs "until next release"), and any changes to the cluster while it's being used heavily leads to instability/unavailability. And many of its features were not implemented great; the SOLR functionality is a pig, for example, and "enterprise" replication is flaky.

On our team, we had a few engineers who could write Erlang, but they slowly moved to other teams, so troubleshooting production issues became a black box of pain. I'm so glad the product we had using it was sunset.