Well it is true that objectively looking ABD might be the most competitive mod. But being the most competitive in the end in meaningless. For example in LoL, having one champion and one lane, playing 1v1 is more competitive in a sense than 5v5 with 120 champions since that brings inherit unbalances to the game. But would LoL be a better game if there was only one champion and one lane where everything would be down to pure mechanics? totally not.

Same goes for this game. As in LoL, where different champions fit different players, same goes for mods in this game. The variety of mods brings most variety of players to the competitive scene, if you limit the mods radically for competition, you are going to lose the people who are actually really good and dedicated to other mods. For example if there is no erthtk or tk in the modlist, I think I might skip on on the whole thing. Same goes for lenshu for some etc.

If you only bring one or two mods to the rankings, then its just who is the best best ABD clan. And tbh, I dont think thats worth much in the grandiose scale.