The mixing and mastering was executed well. When the mix is full, it almost sounds like its played by an actual orchestra. i love the main melody, and the orchestration is phenomenal for much of the piece.
During the quieter section, I felt that there wasn't enough contrast between that section and the other two other than the difference in volume. Also, I think you should have used the most realistic instruments there for the leads since they're so exposed. The melody here could benefit from syncopation, I think. Maybe I wouldn't mind the lack of it if the leads sounded more realistic.
I liked the way you ended the piece, but I think the very last note would sound more conclusive if it was noticeably more powerful than the previous one.
I think you probably could have added some more countermelodies, adornment, and flourishes. The mix sounds full, and the melody is solid, but once I got used to it, i wanted a bit more stimuli.
I really enjoyed this, and I hope you make more marching songs!