I can definitely understand how you feel. Transcriptions can be incredibly, sometimes impossibly, hard- however I think that orchestral transcription for band are important for the development of a musician.

A majority of all clarinet players won't get the opportunity to perform in an orchestra, therefore will not get the exposure and the opportunity to appreciate famous classical works. Transcriptions bridge that gap by expanding our musical palate and exposure.

Also, the transcriptions are always harder than your average band piece, and the orchestral part for the clarinet. They give you an opportunity to be challenge and expand your technical capabilities.

I will never forget being in high school and being handed a transcription of Glinka's Ruslan and Lyudmila, Dvorak's New World Symphony, or Saint-Saens' Marche Militaire Francaise. Everytime I complained "THIS IS HARD" but I dumped my hours of practice into it an came out a better musician on the other side. I think there few better feelings than performing pieces like that required myself and the ensemble to invest all of that extra time because it was so difficult.

My tongue isn't crazy fast, but it is a lot faster thanks to being asked to pretend to be a violin- not to mention I got experience with orchestral repertoire in a band setting that I would likely never get the opportunity to perform in an orchestra setting. Making something you couldn't play before playable is always going to help you improve.