Aficionados of Noah Baumbach’s eccentric brand of hard-hitting family comedies will find themselves right at home in “Marriage Story,” the latest in his resume of accessible mainstream opuses. The rest of us would argue it could have used three key additives: a better script, more focus on the pain, and less insufferable leads. That is not to discredit or undermine the abilities of Adam Driver and Scarlett Johansson, who are competent in the material, but to emphasize the corner they are painted into. Here are two likable actors swimming upstream in a current that wants to drown them in detestable melodrama, and for nearly every scene they occupy shared space, we find ourselves praying for psychological intervention. They are cloying, arrogant, and deluded. Towards the middle act, well before the two come to a head in a heated exchange about unresolved feelings, they are offered advice from brutally honest lawyers as to what steps to take in maintaining custody of their young son. The more proactive argument ought to have been obvious: why do either of them deserve to supervise a goldfish, much less an impressionable kid?