I expect that somewhere there is a WW1 forum where the inadequacies and errors of 1917 have been done to death.
In an oft repeated trailer for 1917 that's appearing on TV at the moment, my eyes saw only the very neat and deep vee-shaped "trench", very obviously JCB dug in dry chalk Salisbury Plain ground that the troops are attacking from, completely different from anything I've seen ever seen of Flanders in film, book or contemporary photographic records of that time. Real British trenches were almost always narrow, roughly dug steep-sided excavations in mostly muddy soil, sometimes wood duckboards along the bottom, but more often several inches of dirty rat infested water over endless mud, German trenches were usually rather more habitable-looking, often with wood-lined sides. Maybe the rather smart trench had been prepared for some special event like The Ideal Home Exhibition. If you want the truth, see a truly remarkable piece of work titled "They shall not grow old", 90 minutes of edited re-speeded, expertly colourised with believable added dialogue, film taken at the time, all genuine stuff from the archives of the Imperial War Museum. Dirty and dishevelled gap-toothed men with wild hair and scruffy uniforms, they were only issued with a single set of Army uniform that had to last for as long as they survived. All the 1917 actors will no doubt be in smart clothing, fresh faced actors with perfect dentition etc. I imagine that a representation of what it was really like would be too shocking for today's audiences,
That said, from what I've read and heard, it's one of the very, very few films from the last 20 or 30 years or so that I would like to see, and I'd be very pleased if my fears expressed above were proved wrong.