Literally the dumbest thing Democrats can do at this point is "oh well, just a weird fluke, we did nothing wrong, carry on 
"
No, the dumbest thing we can do is drastically overreact and completely change our strategy that's won us the most votes in 6 of the last 7 elections.
Did Hillary have some weaknesses? Sure. Should we try to nominate a candidate in 2020 that can win by MORE than 3,000,000, in case the electoral college fluke happens again? Yes. Are things so bad that we need to reinvent the party from scratch? Of course not.
There has been no singular post-Cold War Democratic strategy. Obama's 2008 strategy was quite different from the Clinton 1992 strategy, and the Clinton 2016 was strategy substantially different from both.
That's a really good point that doesn't get that much attention ... most Democratic wins seem to have been because they were in good situations AND had talented candidates, but there hasn't been an inspiring theme carrying them through those decades (like, say, a firm commitment to New Deal liberalism from the '30s until the '70s/'80s). Like them or not, the Republicans have usually had consistent themes during that time period: a strong national defense, lowering people's taxes, basically Reagan conservatism. Trump tweaked it, but he didn't change it nearly as much as people like Sanchez or Fuzzy Bear allege. The GOP is still arguing for what it's been arguing for forever; sometimes it works, sometimes it doesn't, but people know where the GOP stands, IMO.
The post-Carter Democrats seem to be running on same vague collection of the following "truths" that they shove down people's throats (sometimes all of them, sometimes just one) like the GOP being the party of the rich, the GOP causing the great recession, the GOP being super racist ... not saying there isn't a time or a place to call the GOP out for those things (if you actually believe it about the party), but Democrats' campaigns mostly seem to be about how they're the only sane choice, and that's not exactly as inspiring as saying you have a definitive plan to shake things up in favor of the voters.
