I think "grassroots" campaigning is an idea that parties use to dangle as a carrot in front of the eyes of the progressive wings of the party. If you look at any successful "grassroots" campaign in the last ten years you'll usually find someone with deep pockets funding them.

All campaigns take people's time and money to sustain itself, without that funding you're just going to be smothered out. Plus, this isn't a localized problem, it's systemic.

Grassroot campaigns are meant to solve endemic problems, it's not something suitable to change the hierarchical structure of a national political party.

The innate problem with the DNC is that leadership roles are subservient to the people who control the actual funding of the party. People like Nancy Pelosi aren't shot callers because of their "leadership abilities", they are in control because they have long established connections to mega donors.