Canada

Nearly 90 million voters sat home on election day. That's more than either candidate. Disenfranchisement plays a part, but it's more about the complete apathy the American voting population exhibits that's the problem. If even half those people showed up on election day (much less during primaries) the entire country would look completely different. That is a significantly bigger factor than either party shitting the bed.

That being said... Democrats, for the most part, are playing it way too safe. Their leadership is too neo-liberal and too dependent on the status quo to want to shake things up too much, because their main tentpoles (which eerily match the Republicans) revolve around stagnation and a lack of real societal progress. They bandy about social progress with racial, gender, and sexuality policy reforms, but only when it's already well past the point that it'd be possible to enact them. Where it would make them look weak if they didn't do something, and they get quick and easy points by doing the least possible to improve peoples lives.

There's a ton of reps in the Democratic party that want change, and want to see things move forward at a faster pace... but they're constantly pushed to the sidelines by the old guard that has a stranglehold on their leadership. Used as scapegoats when they want to distance themselves from more progressive elements, and fodder when they want to push another milquetoast reform that ultimately changes nothing. The problem is they're hampered by a two-party system. They can either jump ship to a third party, and end up primaried or relegated to pointlessness, or continue on as near-impotent figures that only get soundbites on twitter or facebook.

And that's only on the American "left". The more moderate elements on the right are too scared to speak up lest they feel the ire of the Trump cabal, and end up toeing the line. Even if they feel they're on the wrong side of history.

So there's plenty of blame to go around, it's no one thing or another. The biggest problem, though, being an American populace who refuses to band together and listen to each other, and work for each other instead of just themselves.