You seriously underestimate the depth of commitment that people have to their decisions. MongoDB is undeniably a wreck (though I hear it's been getting better in recent years), but I've come across very few shops who took a look at the wreck and said "This was a mistake". Rather, they usually just say "Let's buy more consulting services, being on the cutting-edge is expensive but it's worth it!"

Everything is a mind game. People have identified their use of things like Mongo as being on the forefront of a developing technology, it makes them feel important and interesting. Try taking that meaning away from them and see how it goes for you. The practicalities of actually using the thing hardly matter.

And is the guy who initially advocated for Mongo going to show up with his tail between his legs and admit he made a mistake? Nope, even if he wants to, that would be a big hit for him career-wise and after our mid-20s most of us have been disabused of our egalitarian notions and know better than to do that.

RethinkDB is the "good engineering" counter to MongoDB. Didn't oversell, worked hard to build a world-class product that targeted the same general product class. Compare for yourself and see what you get by proceeding with an engineering emphasis.

Marketing is mandatory, and developers are naive if they believe they or their field is immune.