For me it tends to be realism vs exaggerated qualities? I think these look like furry characters because they have realistic body proportions, structure, and expressions despite the animal faces and features vs something like Mickey Mouse or Sonic the Hedgehog. This allows someone to more easily see in them the physical features humans find attractive, even a lot of subtle ones considering these characters aren’t sexualized in their official art. It’s not perfect and obviously there are people who have cartoonish fursona’s and there’s cartoonish furry porn out there, but it’s a basic observation