What about a tech that allows us to make a vaccine to protect our kind from the eggs they lay in us?  Or a tech that allows us to make a biological weapon of some kind that can be deployed to exterminate them?  It can be something that can be added to a ship to attack a planet or deployed somehow to attack a planet.

The last one seems like genocide, but is that so bad?  They are doing genocide also by converting most races to their kind.  We have no defense now, so we should be smart enough to develop one or several.  It would take a while and be expensive to use, but it could be worth it in the long run.

Also, the game includes some ideas like executing governors that aren't behaving, so why not genocide?

Or we could all play as the Festron or as the Yor.

Perhaps others will have better ideas.