The current climate of the pure scene might be contributing to the destruction of it. Think about it.. What are you really doing when your intentions of a "rivalry" is to close the other clan? What happens if all power is consolidated in one clan? Strong minded clans won't close, but suffer from some kind of slump especially for not winning the propaganda/rivalry. Weak clans would close and disperse into remaining clans. The cycle will generally repeat itself until one clan exists.
I wouldn't blame the rivalry because any rivalry can essentially boost activity. However, I think the methods should change a bit. Maybe allow your rival to breath a little instead of smothering them every opportunity. Not all of the rivalries from pre-eoc era(main community) relied on starving the enemy of action. Even in cases of crash wars, it always led to uncapped fights between both rivals instead of avoidance. Nowadays, we would call this ragging/ 1-iteming until the other clan calls it quits.
However, I do believe the whole idea of 1 def reset (88 maxed cmb) would be very marketable for singles pkers. This could definitely revive the pure community, but I think the ragging would have to decrease to maintain a good environment.