Aside from all the rules, it really depends on the context the character is in.
For example, Gromit is one of my favorite character designs out there. He's so simple! But SO MUCH or his character shines through in the way he's animated! And his simple design really complements that. There's nothing distracting the watcher from his very subtle expressions and body language. Also, he has a recognizable silhouette which definitely helps.
In my own comic though, A design this simple would probably not work (even if I love it a lot), Because I'm confided to a different medium, without moving image. Even though body language is important for comics too, I simply cannot recreate in a comic the same amount of subtle changes in expression and posture.
If I'm playing a video game though, I have different expectations on the character designs. I had a game art teacher that talked about something he called 'cosplay factor', which he saw was similar to 'appeal' in animation. The cosplay factor was about how cool the character was percieved, how likely you were to see someone cosplay them, as well as how memorable the character design was. I wouldn't say that Gromit has a strong Cosplay Factor, but that a lot of anime and game characters do. The context makes the viewers accept things like, a single very spiky pauldron, or crazy hair, because it's part of the genres. Once again gonna use a fav of mine as an example. I think Zenyatta has a strong 'cosplay factor'. He's recognizable and he fits into the genre. I would not expect him in Wallace and Gromit or Disney, however, and probably would not like him in those scenarios.
But then, if I'm watching a Disney movie, I expect neither a Gromit kind of design, or a Zenyatta design! My favorite character designs from disney come from the emperor's new groove!
They're appealing in a different way from Gromit or Zenyatta. It's a different context again, and what the viewers will accept is different. Not so say that all of these genres can have bad character designs, for example, while Coco is a great movie, the main character didn't have as strong of a character design as kuzco in my opinion, for several reasons. It's not just because it's a different genre, but the silhouette is less recognizable, and even less memorable in contrast to some of the same movie's stronger character designs, like the other main characer Hector. Like just looking at this image I KNOW I'll remember the skeleton dude for longer than the human kid:
So uhhh, TLDR: Genre and context is important before deciding if a character is a good or bad design. Design choices should be based on the target audience, genre, and limitations of the medium.