My macroecon 101 professor, way back in the day, was fond of starting out his lectures by reminding us the "Incentives Matter".
The two parties have been feeding us candidates that range from "kinda bad" to "*expletive deleted*ing subhuman commie" for decades, and people always have this same conversation about least bad or throwing your vote away, and in the end, it's ehat?what? 80% of voters just go with their party candidate no matter what. They convince themselves that this election is too important, or the country is at stake, or whatever else they use to justify voting for a bad candidate, and pull the lever.
The voters of the party offer no incentive for the party to offer a good candidate, much less actually reform the party into something better. The leftists at least realize this and offer the incentive that if they aren't catered to, or at least offered a b9ne, they'll burn down parts of the city. Not ideal, but effective.
Incentives matter. If you don't give the party leadership incentive to change how they pick candidates, they will not change.
On a philosophical note, I reject the idea that you vote against someone, or against a candidate. That's not how our system works. You voted FOR someone. When Biden stands up and says "I got 82 million votes!" there's not an asterisk that 60 mil of them were actually against Trump. When you cast a vote for someone in the US you are lending them your small portion of legitimacy and authority. Own that. If you feel too uncomfortable to say "I voted for [candidate]" and have to coach it in terms of voting against the other one, maybe take a hard look at what you're supporting. Because you ARE supporting your candidate and their policies.