The Democratic National Committee has a policy of supporting incumbents against primary challengers, by making its voter data base available only to the incumbents.

I wouldn't say that the Democratic Party fails to support progressive values, because it doesn't claim to do so, but this is certainly an obstacle to making the Democratic Party worth supporting.

When I support political campaigns, I make sure to support progressives only. Most of them are in fact Democrats, but I don't give to organizations that support them just because they are Democrats.