Making efficient use if mongodb is very difficult but if you build your app and expectations correctly you can get something very performant. For example pre-4.x listing huge collections was unexpectedly extremely slow.
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)