Say you're vegetarian and you get a vote in what the office gets for lunch. You can get either steakhouse meaty meats or pizza. You don't love pizza but a slice of cheese pizza beats not eating. You'd rather everyone order from a sandwich shop where you can choose a veggie sandwich. But that's either not an option or everyone would vote for the other two making your lone vote was wasted because it didn't sway the democratic majority in your favor at all. So you vote for cheese pizza over a mass of brisket or whatever.

Did you get a voice? Yeah, you did. This is what people mean by "lesser of two evils." A minority opinion in a democracy doesn't get to authoritatively decide what's best for everyone. Also, primaries and local elections exist.

Source: Someone with an unpopular opinion on everything

Fixing that requires long-term thinking and action. Something that the Greens and others refuse to do. If Stein, hypothetically was elected, at best, it would be a lame duck presidency because she would have no support from any other branch (except for things supported by Putin).

Local elections, primaries, and congressional seats are needed for actual change. That doesn't have the immediate gratification though of visibly pretending to do something, regardless of if it actually helps.