Politicians don't tend to get much credit for slowing down the rate of deterioration
This OP contains sweeping generalities and I know it, but sometimes it is necessary to view a pattern from a distant height in order to make out its outline clearly, and when you do so shades of gray shift toward black or white.
Since the mid seventies there has been, by every account, a massive shift of wealth from the lower and middle classes to the very wealthiest of Americans. Since the mid seventies the ratio of pay separating CEO's from their lowest paid employees has shot through the roof. Since the mid seventies the inflation rate for higher education and for health care has sky rocketed compared to baseline inflation. Since the mid seventies the affordability of basic housing, at least in most major cities, has pushed home ownership increasingly out of reach and rental costs are not hat far behind. Since the mid seventies job security for most workers has virtually vanished, and dependable pensions should be placed on the endangered species list.
The Republican Party, especially since Reagan became president, has virtually without exception kept their foot on the accelerator furthering all these trends. Democrats have been left to ride the brakes. The economic plight of most Americans would be worse were it not for elected Democrats. But Democrats won't be heaped with high praise for keeping a bad situation from becoming even worse.
I know that the difference between America's two major parties is stark. But as long as the long term trend lines continue as they have for decades, a lot of folks absorbed with the daily struggle of keeping their heads above water may not automatically view Democrats as their protectors. I suspect that lies at the root of a lot of non voter apathy.