Only if you are too stubborn to register as the dominant party and vote in the primary.

Useless because everyone around you genuinely thinks differently from you? Or useless because said 70+ yo retired asset owners with more means to vote without more than the working class?

Big difference in issue. You can't gerrymander a local bill so those kinds of votes are arguably more important than nationals. And you'd be surprised how big a difference a visit with a few dozen of your peers can make to a townhall meeting. That's something we seem to forget until our backs are truly to a wall.