It's a brass thing, it can't be explained. You are a woodwind player and it just seems unfair that brass players have this, but you can't do anything about it. I am a Euphonium player, and I love orchestral music, but I can't play it, because it is not an orchestral instrument. I will say though, I did have the opportunity to play the Planets symphony this summer, and when ever we played, I just felt out of place. The tone and everything just didn't feel like it fit into the orchestra, which is why the Euphonium is not in many orchestral pieces. (I'm drawing to draw a comparison to woodwinds in a Drum Corps). Imagine if Saxophones were a main voice of orchestra, it would not be the same.
All I can draw are comparisons (which some of them suck). If you've ever played something like Pines of Rome for band, you know that it does not compare to Pines of Rome for orchestra in the slightest bit. You can youtube both, listen for Langham's recording of the Wind Ensemble playing it, and then listen to a recording of Pines of Rome by an orchestra. Note the differences and tell me which you like better. I can draw more comparisons... but I think you get picture.
Now, learning a new instrument is a hard thing to do, but it can be done, it is not impossible. Just know this now, you will not pick an instrument that you have never played before and in a few months make the Blue Devils or Cavaliers (or any top corps for that matter), you have to march somewhere else first and may have to spend a few years there before you move up. I have a friend who his freshman year he played Alto Sax and was in the third band at my school. His Sophomore year we had a shortage of Bassoons at our school, so he decided to switch and made the top band at my school, kind of by default. But at the same time he picked up a Baritone in November and made the Troopers Drum and Bugle Corps having only played brass for two months, while still learning the Bassoon at the same time. I'm an All-State Euphonium player, and when my friend came back from the Troopers (so his total amount of time playing Baritone would be about 7 months), he rivaled me in playing and can actually blow way more air than I can. If he were to completely switch to Baritone and not go back to Bassoon, I am almost positive that he would ATLEAST make the All-Region band.
So although it may be hard learning your instrument now, if you spend a whole summer playing it, you will be fine and you will be glad you made the switch. And you will realize how BA brass is and regret ever posting this topic
Sorry for all the unneeded detail... but I hope it helps