Yeah Mongo is 10 years old or so at this point. This article was written in 2015 about decisions made years earlier. It's now reached maturity and stability. It's now "boring tech".
IMO this would be a case where if you're dealing with a relational domain and the engineers really don't know SQL you should either (a) rethink your hiring policy or (b) spend one of your innovation tokens in having everyone learn SQL.
(I have to add the inevitable disclaimer that I actually love JS and do not want my words to be misinterpreted as a cheap dig at it)