Considering the subject, this was a missed opportunity by the film-maker to uncover something much deeper, and leaves the viewer feeling like this just is TV filler, rather than the work of a serious documentary maker. Not a good choice by Mubi curators at all. For a far better documentary which shows the skills of a documentarian I would recommend In No Great Hurry by Thomas Leach, about Saul Leiter.
One of the last shots, possibly the very last, was genius. We saw Cartier-Bresson listening to classical music as we had several times—sometimes eyes closed, seeing things?, enjoying seeing nothing?—but this time we are outside, seeing the world reflected, merged with his living, moving image, in autumnal color, behind him one of his? images, a city view in black and white, merged with the contemporary city in color.
I guess you need to give it at least three stars just because Cartier-Bresson is such a genius. That said, he's not the most photogenic person and the documentary highlights this as much as anything else.
The photographs are amazing. The talking heads are annoying. Possibly you could turn off the sound and put on something classical but you'd still be forced to sit through those yammering heads saying nothing even if this way they do so silently - waiting for the brilliant visions of Cartier-Bresson to fill the screen.