This statement does not apply to third world nations, but it does apply to the US.
If people don't care, then their votes will be uninformed, and the uninformed are easily manipulated by the oligarchy. Thus, when graphing "voter turnout" vs. democracy...it looks like a bell curve...for a while, as you increase turnout from zero, you increase democracy...but at some point, democracy starts to decrease as the "stupid voters" (remember Gruber?) start to vote (e.g., in favor of oligarchical trends...so that the rich get richer). The Dems properly recognize that our traditions in this country naturally place us near the top of the curve (and therefore at maximal beneficial democracy), which is why they are always trying to get the vote out--they want the stupid and lazy voters to participate--their pitch is often directed at the stupid voter (again, Gruber admitted this). But that decreases beneficial democracy.