Usually, American biographical films follow a very familiar template. They tend to focus on a particular moment, usually a challenge or victory, and culminate in a note of uplift or something similar.
Because Mr. Turner is not a Hollywood movie however, there is no familiarity. It spans two decades of the painter’s life, but never revolves around a particular event. So Turner (Timothy Spall) loses his father, is mocked by his peers, and shacks up with a widow. And the camera never stops to sentimentalize any of it.