As long as the military is worshipped in this country, from an immediate numbers perspective there's not much can be done other than appeal to right wingers. Most of them would love left leaning policies but have been conditioned to overvalue right wing symbolism, flag, god, jets in formation, tacticool gear
On the other hand, dems need to lean into a little more populism and much less of the affluent suburbanite schtick
The great divider in this country is money not skin color or ethnic background. Trump's lowest point among his supporters was the trillions in tax cuts to the wealthy, not his handling of covid or anything else. The bulk of his base are not traditional Republicans and dislike the economic policies pushed by conservative economic libertarians from within the GOP. Dems transforming themselves into an economic left party would tear at the seams of the Republican coalition. Of course, they're more likely to keep shifting to the economic right, chasing lincoln project grifters rather than the millions of people in this country desperate for help