I think Steam’s Yes/No system is the best option we’ve got for user review scores. As you said yourself, for most people, it’s either 0 or a 10. And while granularity can help, it’s worthless when it differs on a user to user basis. One users 5 is another users 7. And is the difference between a 1 and a 2 even remotely the same between a 9 and a 10? Probably not.

The biggest argument I could see is that “Mixed” option where it’s neither option, but I feel like that doesn’t really help anyone overall and is just indecisive.