My personal criticism of Hillary Clinton's campaign is that she ran it in such a way that it was both highly ambitious and safe to the point of being incredibly boring. She made some exciting plays for GOP territory (and the data indicated that those areas were within her reach), but then, for example, she went and chose one of the most boring Vice Presidents possible. I don't doubt that Tim Kaine helped her with Virginia, but she didn't focus on shoring up the support the groups she was weakest with: young people. I wouldn't be surprised if she still would have lost even with a more exciting VP, but maybe it would have been enough to convince young Democrats to get out and vote. She also didn't see warning signs in her loss to Bernie in, say, Michigan. Alarm bells should have been going off.
A VP is supposed to counter some of your own weaknesses; that's why Obama chose Biden. Instead, Hillary went with someone who was too much like her (and not enough like her when it came to debating). Even if he was "America's dad" for a brief time, he just wasn't exciting, and apparently excitement is a requirement for Democrats to come out and vote. It didn't help that Kaine let Mike Pence leave the VP debates with his horrific record on gay rights practically unscathed.
She should have either gone all the way with exciting or all the way with safe.
Clinton spent too much time giving the so-called "moderate" Republicans a way out when she should have been tying them to Trump from the start (which, in hindsight, might have only helped them). She also missed an opportunity to tie Trump to Paul Ryan for his burn-it-to-the-ground approach to Social Security and welfare. She ignored Bill and Biden's warnings about the blue wall areas she was weakest in. They warned her, but Mook and co. didn't listen. I get that neither of them are like magic eight-balls, but even if what they said wasn't backed by hard polling data, they're political veterans. I would have thought that their warnings alone would have been worth looking into.
Also, Americans don't like nerds. If nothing else, we now have proof of that. Hillary, Kerry, Gore, and H. W. Bush all lost to people who at least didn't seem wonky. H. W. was the only wonk out of the lot who won a presidential election.
Finally, she made the enormous mistake of assuming that Americans were as disgusted by Trump's blatant racism as she was. She didn't expect that they would, in the case of white Republicans, turn out in record numbers, or in the case of non-voters, that they wouldn't even vote. She thought people would reject Trump like the did Barry Goldwater, but even Goldwater wasn't that blatantly racist. It turns out that, when confronted with racism, some people will take to it like a fish to water, while others will just let it happen. Honestly, if Trump ever decides to go all the way the the Muslim ban and registry, I expect the same result, especially if there's a major terror attack.
I do think that she would have squeaked by if not for the emails and Comey (the latter of which could have easily been avoided if Obama weren't so interested in bipartisanship with people who hate him). Comey should have been let go after the irregular statement he made the first time. Obama also could have taken a more active interest in the DNC over the years and gotten rid of its incompetent leadership, and maybe we wouldn't be in such a shitty situation in the house and senate.
I tend to blame Obama as much as anyone else at this point because of how often he kicked the can down the road. Hillary warned him years ago that he was never going to gain any real favor with Republicans, but he tried anyway. Now his entire presidency is going to be erased by the very same people who have always hated him so much, and millions are going to suffer in part because of his naive team-of-rivals idealism. He's the ultimate good guy to a fault.
When Republicans go low, Democrats need to be prepared to match them. No more being passive. No more reaching across the aisle when it'll get you nothing to show for it. No more incompetent DNC leadership. No negotiating with white supremacists. And never, ever nominate another nerd ever again.