Yes, the women in this movie are talky, but hey, they are writers and words are their medium. Given also that they are mostly graduates of the 70's and 80's the sexual politics/gender clashing thing makes sense.
Someone in this list of comments says that Todd and Trumbo are wooden. Compared to what? Yes, Trumbo's character is reserved, but we see her relaxing as her clothing relaxes -the long coat gives way to sweater.
There is a scene early in that shows the problems associated with low budget- Claire goes to the motel and is greeted by someone. The greeting came off like a question "Hello?" instead of "hello". But by that time I was in awe of Ms. Todd's presence driving the car, sitting on the rocks. I rather thought that the camera was in love with her, following her every movement. And as for wooden, I would say she was fluid and graceful conveying a character in conflict without histrionics. Different strokes.
A good budget, some retakes and tweaking the dialogue all could help, but for a movie that seemingly came out of nowhere it is rather remarkable.