I haven't written a review for a long while, but here's one because you asked so nicely.
I think your main problem in this track is, that your instruments are positioned very unrealistically:
For example you need to position the brass and the drums further away, everything seems to be positioned right in front your face. Get yourself a profile on how an orchestra is positioned, get some real recordings of orchestras and try to position them like that using reverb, panorama and equalizing (the further away, the less high frequencies are heard).
Volume control and proper orchestration: A single flute would NEVER be heard while brass, percussion and strings are playing in that loud dynamic. And there are so many more woodwinds at your disposal you could use to power that main melody. Try mixing various instruments.
There are lots of extensive book about instrumentation and orchestration. Check them out if you want to get more professional.
The structure of the piece is very repetitive, I suggest trying to change the instrumentation (over time) and achieve a different mood with that, different tempi and rhythms and so on. Never repeat the same thing over and over again.
I think I covered up most of everything you should know. I'm still a bit rusty on this.
I wish you good luck and fun with your next track!