The simplest reason boils down to this. In her long history, there's not much to work with.
Not only the average person but like, the average comic fan has trouble naming good Diana stories that didn't quickly rush back towards telling her origin or jumping to her early fish-out-of-water days.
Hell, even this stoic warrior-like persona they keep giving her has existed for what? 20 years tops and she shifts between that and the more friendly optimistic Linda Carter personality?
Sometimes she's a ruthless warrior who kills her villains and sometimes she's the epitome of compassion. The only consistent thing about her is her inconsistency and that's before we get to shit like Donna and the Invisible plane which all results in
>>149243452It's not that people dislike her or don't want to be fans, it's that there's no point in following a character who never really goes anywhere with the story.