I think rules are sometimes made to be broken and that this is very much the case with typography. There are all these rules like fonts having standardised weight etc. But I don't know if it's really necessary or if it should be a basis of judging whether a font is successful or not. Some fonts are design purely to be a title and can't function as body text. Others only work with a certain amount of characters. I think a font should be judged according to what it's trying to communicate and whether it accomplishes that successfully.
Helvetica has been criticised and comic sans is just the worst out of context so I believe we should judge a font on how it works and use the conventional rules as guidelines
Here is an example of some unconventional font's I like, 30 to be precise