What does this have to do with anything? Yes, the Democratic Party is flawed. That doesn’t change the fact that voting Green will make my political desires slightly less likely, and will make my political fears slightly more likely, compared to voting for a Democrat.
Of course anyone can vote for who they like, or not vote at all, no one’s saying otherwise. It’s Harris’s job to earn your vote, and she clearly hasn’t. But pushing third parties as the solution to any problem is going to do more harm than good until we get a better election system. It may feel better to vote for a party that more clearly aligns with your positions, but if they have no path to actually acquiring any power to make change, you’re doing nothing while feeling like you did something. Changing the policies of a flawed party that actually has power is much harder, and yes, there might be compromise or half-measures, but that’s an infinitely more productive path. (More productive than that is doing direct action outside of the electoral system entirely, but both things can be done at the same time.)