All that means is that the general election doesn't matter, and so you need to move your vote to whatever comes before the general election in your district to make it matter.
1. Register for the party that the redistricting and gerrymandering favors.
2. Vote in that party's primaries or participate in their caucuses to support candidates who are closer to center.
Some will object that step #1 is dishonest. I might agree in districts where the district boundaries are actually sensible based on economics and other demographics factors other than party. In districts where one party has redrawn the boundaries to give itself a major structural advantage, they have stolen your vote. Joining their party is simply taking it back. If they do not like that, then they can fix the district boundaries.