I don't think I agree with that. I haven't seen a single Democratic nominee who wasn't also the lead vote getter in my lifetime. Pretty sure there hasn't been one since the modern primary process was introduced in the 70s. Sure you can argue that the DNC throws it's weight behind certain candidates in terms of money and exposure, sure the order of the primaries influences how the later ones tend to lead. And superdelegates will always be controversial. But you can't argue in good faith that the DNC is choosing the candidates for us until you show me one who didn't win the primary popular vote somehow getting the nomination.

Ironically the closest we've gotten to that in recent years was 2016 when Bernie won very few primary elections but won many of the caucuses. The caucuses are inarguably less small-d democratic than primaries but the same people arguing that the DNC rigged those primaries against Bernie conveniently ignore that actual voters didn't want him.

At the end of the day it's still the voters who pick the nominee. And voters can easily pick more progressive candidates if they want to, but the numbers don't lie. Turnout in the primary in 2016 for Dems was 14.4 percent of eligible voters. In the general it was over 40%. In 2020 primary and general participation among Democrats both went up which is good, but the relative gap between primary and general participation more or less stayed the same. Biden won the Presidency with over 80 million votes. He won the primary cleanly, more than doubling second place Sanders' total... with 19 million votes. That's a massive, massive discrepancy.

Saying the DNC hand picks their candidates when younger and more progressive voters can't be bothered to participate is a self-fulfilling prophecy. Or moderates simply still outnumber progressives. Those are really the only two possible conclusions you can draw. I don't really think the latter is true personally so what it comes down to is primary turnout. All the money and exposure and power brokering within the DNC doesn't change the fact that nobody is going into these voters' houses in primary season and physically restraining them to keep them from voting. They are simply choosing not to. And you can't really expect to be taken seriously if you're going to complain about the outcome of a process that you willingly abstain from. That's like going into a restaurant, telling the waiter to surprise you, then being angry that you get served a burger when you wanted chicken. Next time order the goddamn chicken.