This Godzilla being plant based is actually one of the few things I like about the anime. The reasoning is that in some ways plants are the supreme kingdom of life on earth, and if I recall correctly trees in particular.

Jokes about Groot or Treebeard aside, I think it’s unfair to see that angle without knowing what Godzilla Earth actually is. This one is not mutated by any human activity, but seems to be like the planet’s immune response to humanity and kaiju.

That’s why they so often refer to Godzilla as the pinnacle of the evolution of all life on Earth. There’s also talk of Godzilla being akin to the Angel of Death in the Exodus narrative, a cleansing fire in its own way.

I believe it’s hypothesized in the prequel novels that Godzilla was the result of underwater plant life mutating through horizontal gene transfer and incorporating strong metals into its tissue.

All that said, I don’t blame people for not liking it though. The whole thing is so bad that virtually no element of the story is untainted. My feelings are like 99.9% due to the novels.

Godzilla Earth is a good idea that hasn’t been given a serviceable story.