I mean, seriously, if you want to explore the human condition, humans are the way to go.
If you are able to say this, then you have no idea why the sci-fi and fantasy genres exist.
They exist precisely because your statement is false. I mean, why does the character Spock exist?
I think you've got that there backwards.
We often use the term "human" in a very speciesist manner. The human experience is not unique to humans. The human experience is shared by all intelligent life.
We just happen to live in a world where the only intelligent life still alive is humans. But what if we didn't live in that world? What if hobbits were still around? How much could we learn from them about the human experience?
I'll make a very clear example of an element of the human condition that is easier to explore without humans:
Consider the abortion debate. When a human egg is fertilized, it is hosted in the mother's womb until it's ready to be born. However, imagine a species of lizard people, where the mother lays a fertilized egg in some kind of nest, and this egg needs to be actively cared for until it's ready to be hatched.
How would this species of lizard people view the concept of "pregnancy" and "abortion" differently when the egg is not physically connected to the mother's body? And when we compare their views to our own, how well can we justify our philosophical position when faced with this new set of biological facts?
You can do the comparison by having actual humans in the story to compare them to, but I'm going to be blunt. I'm a human. I'm smart enough to make the comparison without the handholding. Additionally, if you have a diversity of species, it's easy enough to have another non-human species which has human-like pregnancies, and then just let that species serve as the human analogue on this particular matter.
