I am one of those who believe Hillary was a _much_ tougher opponent than Biden.
She had a lifetime of political experience, a determination to win, and the Clinton fundraising (extortion) machine.
“The first woman President” had incredible mass media support.
She also had the support of the incumbent President.
Folks here forget just how tough Hillary was....
In practice, she was a very weak candidate, so weak that she was beaten by Bernie Sanders in states where Sanders lost by 10-20 points this time around. That to me suggests that in the 2016 Democrat primary, people weren't voting for Bernie, they were voting against her. And many of those who voted against her in the Democrat primaries couldn't be bothered to vote for her in the general election.