Not discouraging further discussion, but here are a couple of recent threads on the film:

https://www.reddit.com/r/AskHistorians/comments/a7xbbo/in_the_recently_released_documentary_they_shall/

https://www.reddit.com/r/AskHistorians/comments/9ygydc/in_the_recent_wwi_documentary_they_shall_not_grow/