As much as our football team has to beat the odds with recruiting, our marching band has it much worse.
First off, a typical school has about 1 band member for every 100 undergrad, which means TCU should have around 80-90 people in the marching band. TCU manages to get over 200, but the way they do that is by allowing anyone who has ever picked up an instrument into the band. Schools like UT and OSU have auditions and you have to prove you know the music. TCU can't afford to do that and have a similar sized band. (UAPB has a huge band for how big their enrollment is btw)
2nd, most schools don't force their music majors to be in the band. You'd think having music majors in the band would make it better, but it doesn't when half of them don't actually want to be there. Imagine if you were an engineering major on an engineering scholarship, and they said, "As part of your scholarship stipulations, we want you to spend 10 hours a week practicing water aerobics so that you can perform while showing us math equations at the weekly swim meet. And we're going to pair you up with a bunch of people who struggled to complete algebra II." You wouldn't put much effort into it.
Lastly, the actual caliber of players at TCU is much lower than many public schools simply because of how expensive it is to go to TCU. It is much cheaper and much more prestigious to go to University of North Texas if you're wanting to become a professional musician. When most music majors are looking to either take a teaching job (making less than $50,000) or go on to graduate school, it doesn't make financial sense to go to TCU.
All that being said, I think our band does a decent job. I'd personally rather have their performances over Rice or Stanford's.