Yeah, Noah Baumbach is not for everyone. I classify him as an intellectual director, and often times than not, they come across as, in your words, "too smart for their own good", and in turn, become pretentious as a result. I have watched the majority of his films from his debut, and while I do enjoy his work overall, his dialogue can be too heavyhanded and dense. In fact, this is actually an improvement, because in his debut film, Kicking and Screaming, all the characters suffer from verbal diarrhea. That one worked, because it was used to masked the insecurities of the various characters, but it does get annoying at times. He is who he is though. He really has not changed all that much in 20 plus years, and this is just what you expect in a Baumbach film.
Personally, I did enjoy Marriage Story, but that is mainly because I see it as a homage to Bergman's Scenes from a Marriage. That one is far superior, but Baumbach's take is a decent modern update. He also went through a difficult divorce himself with Jennifer Jason Leigh, so this film also feels quite personal, and that helps the overall experience. A lot of the details are too real to be imagined. I had it as a 7/10, and it is certainly one of the better films I have seen this year.
On a side note, New York directors really are something else. I love how their characters absolutely loathes Los Angles. Like with Woody Allen's earlier works, they always have to take a shot or two towards L.A.