If it weren't for humans the universe couldn't observe itself.
First off, humans are not the universe.
Humans can observe the universe, but so can cats, dogs, chickens, and squirrels.
Humans can think about the universe.
But that serves nobody but the humans.
Your claim that cats can't fall in love is ridiculous.
As to symphonies, cats have no need for a symphony. Every moment is a symphony for them.
Humans use music/art as a surrogate activity to reconnect themselves to their severed link with reality.
Cats are always in reality.