I appreciated the parts of The Lost City of Z set in the Amazon. The piranha attack in particular presented the extreme danger of the river and jungle with skilled cinematographic style, as you noted. At times the journey on the river felt almost Apocalypse Now-esque in its hazy, surreal quality. And, the almost comical dismissal of the surely poisonous snake (something Indiana Jones would never do!) is a microcosm of the way Percy Fawcett sees the hazards of the jungle in general – he knows the risks, and he can confidently use his wits to easily sidestep them as they come.
However, the portions of the film set in the jungle started to seem too few and far between as the story got bogged down with lengthy stretches of Fawcett in England. While this was necessary to provide the tension between Fawcett’s desire to explore and his desire to care for his family, somehow these scenes bored. In spite of Fawcett’s insistence that he and his wife Nina were equals, he did not insist that she be publicly placed in a position of honor at the RGS gathering when he discusses his plans to search for the City of Z, nor did he listen to her desire to go with him on an expedition. His dismissal of her desires rarely seemed coupled with compelling evidence that he truly valued her input.
This might be true to real events, but the consequence in the film was that the scenes at home became reduced to dull interludes. The film telegraphs Percy’s often dismissive relationship to Nina and the members of the RGS, and the result is that they were not fleshed out enough to make the England portions of the film compelling. While the audience waited for a return to the jungle, the story was bogged down either by a new quarrel with the RGS, Nina presenting Percy with another child, or Percy marveling at how his previous child had grown.
The sidetrack foray into World War I where Fawcett astonishingly fights side by side with the very same members of his Amazon exploration party was also less interesting than it should have been. You were right here – the most interesting moment during the World War I portion of the film was the scene with the palm reader and the dreamlike fade into the Amazon jungle, but I’d guess that this was a point of artistic deviation from the plain facts of the story on the part of the filmmaker and perhaps the author of the novel.
This film would be better with more artistic interpretation of the source material if it wanted to make a compelling case that Fawcett was truly torn by his desire to leave his family and head back to the jungle. If not, streamline the England story and get to the action in the Amazon.