The biggest problem with the Open is this: The teams that are six, seventh and eighth realistically have no chance to win a state championship, whether from the South or the North. At the same time, if they were dropped into their enrollment divisions, they would have a very good chance to win a state championship.
So what's the motivation to be in the Open? Well, nothing…
The only way to change this that I can see is to make the Open special. That is, give every open qualifier a huge banner to hang in the gym, and some kind of tangible reward for players or the school. At the same time, the other state championships should be downgraded to division championships, so the only "state" champion comes from the Open.
But as long as the state championship banner that hangs in the gym is the same for the Open as it is for Division IV there's no motivation to play in the Open unless you are a nationally ranked team that can go head-to-head with programs that have multiple Division I players, and most likely a couple of Power 5ones as well.
What northbayguru is referring to is that both Cardinal Newman and Miramonte would stand a pretty good chance to win a state championship if they are placed in Division II or Division IV, respectively. In the Open, they are major underdogs, as Mitty is simply too good. (Mitty may be too good for anyone in Northern California, not just those two teams.)
Maybe, though, if qualifying for the Open meant something special, there wouldn't be this race for the ninth seed in Northern California.