For me, Homo Sapiens are just one other species in the Duckburg melting pot. Too many memorable characters like Dr Creepy-Eyes (from Ancient Persia), Witch Hazel, Yen Sid or Madam Mim are humans for one to disregard them.
Agreed. I actually like the idea that in the world of the Disney comics, many different species of the genus homo co-exist - homo sapiens, homo canis, homo anatidis ... that way I can think of them as definitely human without completely disregarding their animalistic features.
As others mentioned there are differences between realistic looking humans and caricatures too... the former do look weird when just put into stories, but if there's a stylistic/conceptual reason for them to be there (like in "Dangerous Disguise") it's okay to me.