That’s mostly a question of how one chooses to define “intelligence.” For the purposes of this type of discussion it’s usually equivalent to “whatever humans have that other animals don’t.” We’re looking for something that would be relatable to us, probably the minimum requirement would be the ability to communicate with them at the same level of robustness that we can with each other (edit: or a recognizable demonstration of mastery over the physical world to a level that meets or exceeds our own).
It’s true that other terrestrial life forms possess some capabilities that we could call intelligence, but then we would just need to use another word that defines the special human je ne sais quoi.
Probably the most relevant difference is humans forming prestige hierarchies alongside dominance hierarchies with larger brains able to store more of the resulting cultural accumulation being partially downstream of that. Knowledge transmission is always imperfect but if people try to learn from the guy reputed to be the best flint napper you can support a lot more technology than if everybody just learns from their parents.
Learning from non-kin isn't unusual in the animal kingdom. Monkeys seeing other monkeys drop a mix of sand and grain in water to separate them and then copying that is a classic example. But deliberate teaching of non-kin and the way we use language to help with that teaching is pretty unique. An octopus might have smarts comparable to a feral human, but not to an acculturated human.
It’s true that other terrestrial life forms possess some capabilities that we could call intelligence, but then we would just need to use another word that defines the special human je ne sais quoi.