As many have probably already said, one of the few things that makes the horrors that a society goes through is humor - and "Lethal Kittens" is an example of this. This film isn't for everyone. For instance, I don't think that someone completely unfamiliar with Ukrainian culture or the atrocities of the Russo-Ukrainian war in Eastern and Southern Ukraine will really get the jokes or understand why it's worth joking about. If you see a negative review, that's probably why. However, for its audience, the film is a bit of a release... It "says what everyone's feeling, but don't know how to express..."
As far as the name, "Lethal Kittens" is a rough English translation of the nickname that volunteers use for the soldiers that they support. That's one of the important things to understand for the context of this film. Especially in 2014 and 2015, the Ukrainian army was so poorly equipped that villages had to band together to buy bullet-proof vests or helmets for their sons that were being sent against the Russian army in Donetsk. Volunteers were essential to the survival of Ukraine, not just the soldiers on the front lines. Because of this lack of resources and support from the government, the soldiers often felt abandoned by their higher-ups (this is seen in the film). This is still true today.
If you've gotten this far in my review and are a praying person, please pray for this conflict, especially for all of those caught up in the fighting.