I feel like one of the issues with the film's tone is that it was 100% on Taika to create it, because the book that Jojo Rabbit is very (very, very, very) loosely based on is... completely not a whimsical satire do-ho-ho-in-the-face-of-Nazis film. It's a creepy dark book that combines a Hitler Youth character with a growing lustful obsession that reminds me of that old book & film, The Collector, about a young man who kidnaps a young woman. It's... a completely different tone.

So almost everything about the film had to be built from scratch, aside from the basic premise.