You are assuming the goal should be "prioritizing accuracy of the seedings". It also seems you are measuring accuracy in terms of determining which teams are the best. However, there are trade-offs in life.
While accuracy and excellence are commendable goals, so are objectivity and transparency; particularly when administering a program that should promote fairness. What if rather than prioritizing those teams that are better, the seeding system is meant to reward those teams that had better regular seasons in relation to their peers. I have no doubt that Wheaton-Warrenville South (a 5-4 team that finished in fourth place in the DuKane Conference) is a better team than Whitney Young (a 9-0 team that finished in first place in its conference). But I do have doubts that Wheaton should have been given a better seed than Young in the 7A playoffs. Young had a remarkable season relative to their peers, and giving them a 1 seed allowed them the opportunity to win a first-round playoff game. Wheaton-Warrenville South had an average regular season in comparison to their peers. If teams are allowed into the playoffs based on the relative success of their regular seasons, is it not consistent to then also seed them on the same basis?
There is also some value to having excellent games in each round of the playoffs, as the current system allows, rather than saving all the best games for the last two weeks of the playoffs.
With all that having been said, I am rather partial to the pursuit of excellence and then rewarding that excellence. Clearly CalPreps or Massey or several other systems would do a better job of measuring excellence/ability than the current system of seeding. An objectively designed (and transparent) study would quickly prove that to be the case.
I personally find the trade-offs in this discussion to be quite balanced, and consequently am comfortable with any of the seeding methods that have been discussed in this thread. If pressed, I would fall back on the principle that frequently the best solution is one that melds the best of the competing alternatives. As has been offered by others in this thread already, I would seed the top eight teams based on a computer rating (after having studied the various computer systems for accuracy). The remaining 24 teams would be seeded using the current method.
The main point of this message, though, is to suggest no agreement will be found in this thread (though it is fun to discuss). The reason for that is the fact that there are trade-offs, and each of us will evaluate those trade-offs differently and subjectively. Under those circumstances the best course is to have a vote, and that is what the IHSA (a member driven organization) is designed to do. So far, that process has resulted in the system we currently have. If, at some future point in time, enough members become dissatisfied with the current system, they will vote it out and a new system will be implemented.