Children don't grow up in a few bite sized chapters you Dumbos, especially not immortal shapeshifting god orphans.
It's natural he doesn't understand yet, but he already has the boy's heart, eventually, before long I'm sure, he'll gain those proper emotions and an understanding of them, his future is endless, and considering that no one is born perfect and he was born as a tiny ball, he's already come really far.
In any case, he already occasionally showed flashes of one most beautiful emotion from the very start, empathy.
Don't worry, he's definitely alive, what'd be the point in the manga if the immortal was just dead inside. And even regarding intelligence, there is already occasional nuance in his actions.
This is about the beauty of life and living beings in every sense and sometimes life is a bit freaky, god boy'll evolve and grow out of it eventually.
For now, as humans, we're basically the collective parents of this amazing creature with infinite possibilities, so let's not be cruel.