As in you need to switch your entire database system or make a bet on this completely new player instead of battle proven tech, because with relational databases schema migrations are hard. Among a bunch of other questionable claims.
Sure if you take the vanilla databases without their ecosystem, there is some merit to that, but I don't find it a very practical argument to ignore all the tooling and workflows that do exists and are used by people.
When MongoDB first came out, I was eager to check it out. I was using mainly Django with Postgres at the time, but had my career start on ZODB, an object-oriented non-sql database created in the late 90s. So I was hopeful that MongoDB could give me the best of both worlds. One of the reasons I backed of Mongo very quickly was the lack of tooling as soon as you have something resembling a schema or relationship and you'd want to change it.
There's your answer, no? You've got specific tools and workflows you've designed to work with your database in a specific way. You can't just take one workflow and substitute a piece of another workflow and expect it to always work. Your tools and processes would be as useless for me as mine would be for you.