You need to join an organization that is doing more than activism theater. This is surprisingly hard to do. For one thing, because of COINTELPRO infiltrating leftist groups, there have been a couple generations of activists who have never known anything other than activism theater. For another, our hyperindividualized society tends to disincentivize collective action.

It's probably easier to find an organization doing good work in one area than one looking at the whole picture, so if there's an issue you particularly care about, you should probably compare the leading organizations focusing on that issue.