His message is flawed and he's flawed.
Hillary Clinton has been committed to change her entire career. She's been committed to connecting to voters since she was a teenager knocking on strangers doors on the south side of Chicago. Just because a very loud segment of Sanders support is willing to ignore her history doesn't mean all the millions of real people that have voted in this primary and caucus season have as well.
Yes, some believe that some speeches Hillary made years ago are a big deal. She's made three decades and reams of her financials and tax returns public. That's much more than Sanders has bothered to level with you or anyone else with during this campaign.
And, yes, that same very loud segment of Sanders supporters want to give Sanders a pass on a political career based on talk with few results.
Sanders ran a lousy campaign based on big rallies and big promises instead of a campaign about substance, policy, and connecting to voters across the entire political spectrum. He focused on talking to people who already agreed with his narrow political views.
That failed. Today, it's over.