I think that's precisely the reason so many people find it offputting. A baby is not an accessory - it's creepy to see it treated as such. Of course giving it a name, personality and separate emotions would require more work; however, there's really no reason to have the joeys in the first place. A female kangaroo doesn't need to be shown with a baby any more than a different species animal. To me it's not much more than a poorly done gimmick
They could've made it worse and make it lifeless. Or it could just blink.
That's kind of what female kangaroos are known for though. It's the most known marsupial and a pouch = a baby. Yeah there's other marsupials but kangaroos are probably most iconic. Ones without joeys are immediately distinguished as bucks (males).
Picture association is strong.