I haven't seen this yet. It's hard to imagine that a keto diet would not be good for just about anyone.
Whether it can positively influence serious pathologies is a much more tricky question and needs a lot of good research. It would be going way out on a limb to claim that it can cure cancer without really good evidence to back up the claim, even though there is a plausible scientific theory about glucose and cancer cells. I'm not a biologist or a medic so I can't make a judgment about that. I'll try and watch the film though.