It's a shounen adventure with fairly good animation and nice watch. I do not expect it to be perfect.
Kanata certainly is one of the most of not the most suicidal of all, young testosterone male style.
But the logic behind is action is in line with the pitch. Spores surely interact with antidote mushrooms.
If there's no animal infected, there's no need to expand energy to grow antidote mushrooms.

Lower your expectations and have fun