You can't make things better while they're getting worse.

Yes you can; in fact that's usually what happens. That aside, no reason not to vote Democrat, but it's simply not a viable way of holding back fascism. Also, lesser evil politics can and does directly contradict with direct action (see: Gaza protests during Biden's term), so "let's just do both" is only remotely viable when the Democrats aren't in power. When they are, you end up having to choose between supporting them and denouncing their ghoulish actions. We've seen this movie before.