If democrats in the US vote for stuff like Biden, then they’re not voting for any radical change

I don't exactly know the details, but weren't there accusations of meddling from the DNC that stoppered Sanders' chance of securing the nomination, and a belief among some that he might have won the nomination if it had been a free and fair primary process?

In other words, it's possible (though by no means certain) that your sentence above works if "democrats" means "the DNC and the establishment of the Democratic Party", but not if it means "people who by-and-large support the Democratic Party".