As someone sympathetic to liberal policies... Dems have to do what Schultz is criticizing them for in order to win elections. Far too often they get bogged down in technocratic explanations of why programs are important and how we're going to be responsible and pay for them, as if they're appealing to some fiscally minded bloc of independents. The problem is that group, to the extent it exists, is already deeply skeptical of most liberal policies they're having explained to them by Dems. And the Democratic base doesn't get enthused by the technocratic talk.
You saw it in the 2016 primaries: People were super fired up for Bernie's plans, whereas Clinton criticized him for how he proposed to pay for them. Guess what? She won the battle but lost the war.
Meanwhile, Pubs have explained away things like their tax plan using funny math and stuff like "it'll pay for itself!" They similarly tried to mislead people about the effects of their healthcare plans.
I'd like to see the Dems just cut it loose and focus on big, bold proposals. The group of people that vote on fiscal responsibility appears to be shrinking. If 2016 taught us anything, it's that people will vote for even fruit loop ideas if they get pitched right - and they'll worry about the specifics later.