I supported Bernie Sanders, and the DNC used every cheating dirty trick in the book to make sure he failed. If Independents had been allowed to vote in all the primaries, he would have won.
Now, why would the DNC have to cheat? They wrote the rules! And the rules say, they can nominate whoever they want. The superdelegates are there for just that reason, to overturn the primaries if the people don't pick the one they want. The primaries are only advisory. The results are not binding. This is by design. The RNC has slightly different rules for itself, but the idea's the same.
People complain about how unfair the primaries are. Yup, they're unfair. They're unfair by design. The DNC and RNC are both private organizations that can do as they please. Don't like it? Go vote for a different party, one with internal rules that you like. Try to vote for someone promising election reform so we can get rid of this whole rotten system. Not that anyone promising election reform has a snowball's chance in hell of winning. If they had any way to win in the current system, they wouldn't be trying to reform it.
Yeah, it sucks. All of it.