Reality check...The schools that do well in marching band also do well in the All-State process, Solo and Ensemble, and in the honor band process. I could name a couple of what may be considered "inner city" bands (although they are corps-style) that do very well in marching band. They also do well in the All-State process and the other events mentioned earlier.
It is no secret that corps-style is the way to go and there is a certain basic formula that must be adhered to if you want to compete. UIL has been holding back the sheets to try to give the show bands and military bands as much of a chance as they can even though they are such a small minority of Texas bands. The sheets are changing now because the apparently the majority of people want something different.
Want to do better in marching band? Here is what I do:
Go to TBA and go to every marching clinic offered.
Use the All-State process and Solo contest to build the individual players in your program. This means more than just signing them up. You have to work with those students outside of the school day. Without the players you won't score well.
Use the fall to develop your sound and technique that will allow you to play harder music in the spring.
Use your spring semester to develop your sound and technique for the fall.
Recruit like crazy so that you have the kids that you need. This starts at the MS level.
On your "non-State years" go and watch prelims and finals of the class above yours. See what the trends are. If you want to compete you have to play the game.
During the region clinic concert time ask other directors in your region if you can meet and discuss what they've done to be successful. Most people are very helpful. I've both asked for help and been asked and I can tell you this has helped me a lot.
Ask questions on the yellowboard. Ignore the clowns and don't worry about stupid responses. Let those slide and look for the helpful people. There are many on here.
Hire, if possible, a clinician. If not, ask if you can trade some help with sectionals or other event to have someone who has been there help you. The clinician needs to be more for you than for the kids. They are only there an hour or two. If you learn to see and hear things the way they do, it will make you a much better teacher and your group better.
If electronics are an issue, ask questions here, on facebook, or contact a local church that would have sound guys who can help. When I graduated from college I didn't know how to plug in a microphone. The internet and other resources have been invaluable in learning to get the most from the equipment we have.
The people that are consistently getting to the state level (in honor band, marching, or have multiple all-staters) are constantly working to build their program. It takes way more time than most people are willing to give and everyone needs to decide if that is for them or not. It doesn't make you less of a band director if you aren't willing to do the extra things. But, if making it to the state marching contest is your goal, you are going to have to do more than your competitors are willing to do.
Each year there are a few people who take disappointment and use it as motivation to get better at their craft. Unfortunately, the other 98% find it easier to complain on the yellowboard about the rigged system, how bad UIL is, how the judges are all wrong, etc.