Truth be told, it used to be "The Blue." Now it's MC and LA. Rice and Rita aren't even operating on the same stratosphere anymore.
Honestly, Naz would be the most logical choice to create a permanent triangle and then other schools can rotate to take the fourth spot. Perhaps some combination of Marist, Ignatius, JC, PC, Rice, Rita, and maybe SF.
But there is no more "traditional Blue." Back in the mid-2000s to 2010s, you could guarantee some slobberknockers with Rice and Rita when they ran into MC and LA. Now, unless something changes, those two schools should be the prohibitive favorite over absolutely everyone they play. Their enrollment numbers and athletic draw over 30 miles dwarfs what any other institution has.
A good goal for Rice and Rita now is honestly to stay within a few touchdowns of those big two. Even staying within 3 scores is a sad moral victory. And Rice is busy trying to not get running clocked by Batavia.
I would keep MC, LA, and Naz connected at the hip for now. I know Naz isn't really super close to those two, but they are the most steadily strong program that would have a chance to stay within a few scores consistently.
Naz is currently the flag bearer for the mid size private schools. A spot formerly trumpeted by JC, PC, Driscoll, Montini, SHG, etc. That level of mid-size private dominance has always been there and people will always complain about it. But the IMG like appeal of LA and MC is what will likely be the thing that upends the entire IHSA system.