You have an amazing starting point as a composer as seen by your attentive ear, diligent production/planning, and arrangement skills. Very good arrangement section-wise, and you also have the appropriate inst. sections playing at the ranges they need. A very dynamic, Miyazaki-esque piece wtihin the realms of film and gaming.
As for constructive feedback to help you on your composer journey: (EVERYTHING IMO!!!!!!) (Sorry for word vomit)
I would've loved it you repeated that same intensity again at around 1:30 with the drums/cymbal, and maybe introduced a countermelody in one of the other instrument sections. It's intense at that moment, but it diminishes pretty fast afterwards. I think the brass does a good job selling the intensity at first, but you just needed a bit more expression within the brass arrangement. Your 2nd breakdown at (2:08) is pretty good, I would just add a solo bass instrument to help fill up space.
Also, when the section at 1:30 starts, you could use the piano to play the melody + ascending/descending arps to embellish the dynamics of the strings. In this instance, the piano is only playing the melody with the strings, but could be used to create a fuller, dramatic sound. Harp could work too, flute flutters, certain sections (within their range).
I think the stark volume difference from 1:40 to 1:43 is a little bit too much. In isolation, it sounds amazing, but examining the dynamic range of a piece is important to finetune for multimedia. You can play soft, but just have the instruments a bit more audible in those sections via automation. The timbre of the instruments should be able to replicate it well.
Overall, I think you executed your idea pretty well! I think you meticulously dissected the picture very successfully, and painted a soundscape fitting your theme of impermenance. I wish you luck, and I'm looking forward to your promising composing future :)