Someone decided to make it in a language most audiences would not understand, and not bother with subtitles. And chose Rhaeto-Romance, but it is unlikely that any variant of Indo-European would have got so far west 5300 years ago.
Not understanding anything spoils the human interactions.
It is also excessively brutal. The aftermath of a battle would have made a lot more sense.
People of the era probably had a lot more social interconnections than are shown.
Someone is hung up on the idea of Heroic Individualism and wasted a grand opportunity.
Firstly, I watched this film knowing very little about it and I think that is the best way to watch it. All I knew was the use of the Rhetian language believed to have bean used in that region of the film's setting around 5,300 years ago. The film tells you this at the start and the film also tells you that there are no subtitles because the film makers believe there isn't a need, and it is true in my opinion. There is very little diaglogue in the film, all the information you need is presented visually.
It's best to stop reading here if you don't want to know anymore but if you do, I promise the following does not contain any spoilers:
This film is inspired by the Ötzi mummy which was discovered in 1991, high up in the Alps near the Italian-Austrian border. All of that is fact along with the facts that the man lived around 5,300 years and died a certain way. The rest of the fim is a plausible tale given how the man died so high up in the Alps.
Please note the film is NOT excessively brutal. There is brutality in the film, but it is not gratuitous! For example, humans are still stabbing each other in 2019, what do you expect happened 5,300 years ago!?
A stone age man struggles through the frozen Alps seeking revenge for his murdered family. All the men in this seem implausibly old and their home tribes unsustainably small. There is no comprehensible dialog only unrecognisable words and grunts. Still, it was better than films of similar ilk I have seen before.