The Doriki system was there to show in an explicit way how the CP9 members ranked in terms of their strength. Oda didn't include it for it to be utterly irrelevant only because you guys spend your time overcomplicating it with eight thousand nuances so you won't accept that he portrayed Sanji to be way closer to Zoro than you want, even though that narative has been there forever both directly and indirectly.
When you have the guys uncapable of catching a bigger dinosaur than the other, or Mohji and Cabaji arguing like them and fighting to a draw, or their zombies clashing equally, now both taking on Kaido's strongest men, being repeated as two big shots and Luffy's wings, and so on you may get the hint that they may not be equally strong, but way closer than you want to accept.