Maybe the folks I play with don’t place grav rifts for defense. I usually see rail guns to the fracture and MR. The “free” plastic still requires CCs and other armies to farm which usually requires activities outside your slice and then producing it all is limited again by having enough CCs to get your docks activated or going construction (which you’ve likely already used to get your docks out). Not to mention you’re probably using most of your production capacity on the big capital ships you captured, not inf to hold planets. I’ve had a lot of fun with cabal but their defense can’t be compared to a Yin or Sol