I don't think it's accidental that the only non-real "animal" in the story is the dragon.
They can do magic. Our main dragon boy can fly, his mother can enthrall people with her blood, apparently there are dragons who breathe fire, and now this earth dragon can do magic moving root shenanigans, creating a massive digestive system disguised as a peaceful forest.
It's not without reason that the other animals have a vendetta against the dragons. The dragons are massively OP. They destroy the natural animal populations and treat "lower animals" like filth. The only reason why Hekidou is slightly nicer to lower animals, is because he was raised by one, rather than raised by other dragons. If he had been raised by his mother he would certainly have ended up like her.
But the dragons' direct abuse of the lower animals isn't the only reason why they are hated. It's also because they wage war. The water and fire dragons waged war against each other and razed the lands, then had a ceasefire and split up. But the water dragon population went into decline until they started infighting and cannibalising each other.
Why they went into decline is unclear, but the fact remains that even within the same species of dragon, they will wage wars.
Other hateful traits of the dragons are seen in the earth dragon in this chapter, who's basically raising livestock. And interestingly, the majority of the livestock animals are overly docile, incapable of surviving in a natural environment.
Hekidou's mother is up to similar mischief, and enslaves wild animals into work-animals, either through sheer threat of violence or by 'breaking them in', which she does to a bird of prey. You might be interested in looking up how falcons were tamed irl, historically.
The dragons are destroying the natural ecosystem through overconsumption and war, have powers beyond an animal's scope of reason, treat the world around them like filth, and while vying for limited ressources, obliterate themselves.
The dragons are humans.