She's obviously the worst Democratic candidate since Dukakis.
Dukakis lost to Reagan, who despite being probably the worst president since Coolidge on policy matters, was considered a great and moving orator. But Hillary Clinton lost to Trump. I think that pretty much says it all.
Hillary Clinton knew how to talk to upper-middle class people and rich people (particularly with college-educated careers), and she had a history of building inroads with (particularly Southern) black communities. She was very good at talking to people in corporate and DC culture, and she especially knew very well (undoubtedly from personal experience) how to stoke a lot of women's resentment at having their gender used against them. So the media mostly adored her, a lot of older feminists loved her, corporations/banks/Wall Street largely loved her, and the kind of people that fall into those jobs. But in terms of broad appeal? Well, as far as the stats I've read are concerned, her ability to bring other groups to her side was basically non-existent. She didn't understand and didn't really care to understand how to people to non-core Democrats in the Midwest, the South, and the non-coastal West. I'm not sure she even understood that it was possible to appeal to rural voters, and the total absence of support for her in these areas (despite Obama's strengths in these areas) was clearly
another major error. It didn't help that she spent a year ****ting on important groups in the Obama coalition, particularly
youth voters, which was probably her largest error because they are particularly important for building momentum. Her only strategy to deal with any of this was "Trump is a terrible human being," which was successful enough to give her 3 million more in the popular vote, but it basically just cause a lot more people in New England and CA to vote for her.
Additionally, she also had no core message ("I'm With Her" is a really stupid campaign slogan), and I think that was another component of what really killed her campaign. Although, even if she did have a message, I'm not really sure why she would have come up with the right one; she admitted she couldn't figure out why people
were flocking to populists which is pretty damning. This I think is the core reason for her failure in 2016: She didn't really understand that half of the country is really hurting and really pissed, and couldn't figure out any way to motivate these people to get to the polls.