I agree auth is a huge success, but no alternate DB support is a not starter for most I imagine. Any other non relational DB support would be a huge win, most people that I have talked to are blocked by Mongo's license.
How in particular are they blocked by Mongo license? It's AGPL but it only applies to changes made to the database source code itself. It doesn't impose any requirements on your application if you are just talking to Mongo over the wire.
It is not unheard of for businesses in both the public and private sector to not allow AGPL code or use of applications released under this license.
For example, I worked at a public library for years, and the policy was no AGPL, even if we had no intention of touching the source. Same for a local university.
