You suggest we under-estimate animal intelligence, which is the same argument I'm making. The reason we underestimate how hard human intelligence is to solve is that we underestimate the animal part of our reasoning, animals can't play chess or do math or write sentences, so when computers do that people assume they are smart like humans. But that assumption hinges on the animal part, like navigating a forest, identifying plants to eat etc, isn't a fundamental part of intelligence or that it is easy to solve in comparison.

So yeah, underestimating animal intelligence is a large part of it, I agree with you.