>they vote against their own interests because of partisan issues/politics.

This isn't like some temporary blemish on democracy, it is democracy. People have different opinions (partisanship) about what ought to happen in the public sphere (politics) and outcomes are dictated by the people's actual votes rather than expert opinion about their best interests.

I'd be down for a technocrat philosopher-king, but that's not the world we live in. In fact, technocrats are being soundly rejected by both left and right.