The problem with your argument is that it doesn't hold up. It sounds like you are saying that PS clans are not as good a Xbox Clans. Neither have any advantage over the other and they both have skilled players (and a lot of not so skilled players too). You need to start stating some facts and not just your opinion and maybe even back up your argument with some evidence.
Whether a clan is cross-platform or just one platform, it all comes down to how much your clan can play and compete against the other 7 clans in your clan war. The 8 teams are matched up based on size, amount of play, K/D ratio, and W/L ratio to make it more competitive and so there isn't one team that just outright dominates (most of the time). The cross-platform doesn't matter here as they are still added into the calculation.
I guess I don't see or understand your logic as to why cross-platform needs to go away and what benefit comes from removing it.