you could be participating in your local elections. You could vote in primaries. You could be concerned about who's going to be your next local county sheriff, local zoning board officer, etc. You can get involved in the local political parties and affect them on a local level. (this is assuming that you already vote in all off-year elections, and already vote for president)

HN sees only the top level of the abstraction and assumes that the system is a lumbering behemoth incapable of change. Pushing the system from the bottom, it's actually quite capable of very abrupt change. Unfortunately, those methods of change require copious amounts of time, and will probably replace or supplant much more enjoyable hobbies you'd rather have.

In previous eras, this was considered the burden of citizenship...

For a simpler answer: Call your congresscritter. They're actually very responsive to phone calls and real letters. It's not hard to do.