There are many talented actors who have studied minimally or a lot, but don't rely on technique when they perform; and there are a few who have never studied formally, but are talented enough to not make the error of indicated depiction of a character with the result of either showing us their idea of the character or reading the script's dialogue narratively rather than acting dramatically.
I've written elsewhere on my blog that talent is a variable, but that technique is not. I don't think there's any substitute for technique regardless of the actor's innate talent, and I think Ms. Johansson has demonstrated my POV very well in several scenes in Marriage Story. Two scenes from the film demonstrate this: In the above scene, when her partner commented on her hair in a very intimate, personal manner, the thought that preceded her verbal response conveyed physically the irony that although they were no longer in such a relationship, he didn't seem aware of it, was dramatically conveyed and appropriately performed. Note that her body language and words conveyed that idea.
However, in the following scene, Ms. Johansson performed her monologue narratively. Note that every sentence of her description of her marriage seemed to be known to her in advance, and she rattled off, without hesitation, disparate events consecutively that had taken place over a period of years. Many actors who do this will frequently shake their heads back and forth while they're speaking, which I interpret as an attempt to connect to the idea. Note how much Ms. Johansson did that as well as physically shake herself during her monologue. I think she was trying to connect to the images of her narrative description. Each sentence of that well-written monologue needed a thought to precede it, a reliving of each incident - a reaching for the words to describe the images of those disparate events. In addition, compare the relaxed voice placement in the first scene as opposed to the tension in her voice in the next scene.
In addition, in the following scene, she performed the scene correctly until her last sentence. Both men were trying to convince her to participate in a way she no longer wanted to. They were critical and ignored or weren't sensitive to her resentment and pain. She needed to hurt them, insult them in return and escape. The actor needs to prepare the action/verb for each individual sentence. To insult or even something stronger for, "I'm gonna go if you're just gonna sit around and suck each other's dicks," needed to be laser beamed at each of them. Instead, "...suck each other's dicks" went into the air, instead of being the piercing dagger it needed to be.
An actor who understands and uses technique in rehearsal and performance knows how to avoid the pitfalls of uneven performance.
