I think there's an important distinction between the idea of a "worthy opponent" and the thought of "someone I'm excited to see my team play."
Beyond that, as decent or worthy as Iowa State might be, they're still a team that Texas must beat, in order to return to being the kind of football team that competes for conference and national championships. Texas fans are going to use this game as a litmus test, and if Texas doesn't win it, they're going to believe that nothing (or at least, not enough) has changed from last year to this year. This coaching staff already failed their first such test against Maryland, in miserable fashion. Texas fans aren't going to, and shouldn't, accept bad coaching decisions and bad player development.
So although I understand what you're saying, I actually don't agree. Nobody should take Iowa State lightly. And yet Texas absolutely must win the game, for many fans-- including me-- to believe this coaching staff has any hope of moving in the required direction.
You can lump me in with the t-shirts if you like, but you'd be absolutely wrong in doing so.
I believe that the Maryland game needed to happen.
After all the spring practice and summer bonding, the players knew what their coaches had been saying. They heard the words and went through the motions, but when it came time to fight, they forgot it all and reverted to what they did last season - and got last season's results.
I believe the coaching staff reviewed that tape with the players and then showed them practice. Two totally different tapes. Against SJSU, they trusted their coaching and their training, but it was SJSU.
Watch the USC tape. You see a defense that fits all gaps, then a streaking 46 rockets through and just kills the ball carrier. That's not a man who's thinking. That's a man that knows his role and uses his athletic talent to execute it violently. I was gratified that, even when USC hit a couple of big plays, the defense didn't lose composure. They kept playing their roles.
One game of fierce defense is unique. Two can be chalked up to a "name" opponent. A third such performance would a habit.
All this to say yeah, you're right. The ISU game is important to demonstrate that Texas didn't just overachieve in a loss to USC, and things really are different.