What's your alternative?

Do you have a ready-built national organization that can be successfully co-opted to supplant the DNC i dont know about?

DNC isnt just a sunk cost, its an established civic investment. Unless you think the whole system is going to collapse overnight, a takeover of an existing party is the quickest way to get real change. And if the DNC is rotten and needs to go, we can best do that from the inside.

Every "third party" either merges into a major party or devolves into a vanity party, because the only positions that matter electorally in a winner-take-all system are "i suooort the current person" or "i want them out of office."