Hi!
I listened to your finale days ago but didn't find time to reply so I'm re-listening. First of all I don't think any criticism or output in general that I'm going to write in this comment will be of much use, since I myself haven barely composed 2-3 works for many instruments. The sound is very good —except for the tremolos, maybe— I must say. In order to prevent a dense message lemme summarize what I have been thinking while listening & reading.
• Despite the lack of well-defined structure, you know your game: you seem to be comfortable in transitioning between calmer sections that you make interesting by themselves and more vivid ones. Your music, at least to my taste, flows despite of that "flaw". You made it like that though, so if you are already convinced of the result you got, I personally wouldn't change a note. That said, I would need to listen to the whole work to see how much of a finale it is and how much it relates with the other three movements, because right now it tells a story to me that begins and ends quite decently...
• Yeah, regarding the final part that I would definitely call "The unknown soldier's trumpet solo" quoting @Krisp's words, I believe you could have extended there a bit more, I just felt it ended a bit too soon, I didn't perceive a proper preparation (considering again this is a finale and the ending of a 14 minutes piece) but perhaps it's just me, I am often very nit-picky with ending sections sorry.
In summary, you have the tools, you have the sound and you have the skills needed to combine all of that as we all have listened and make a very beautiful and promising movement. Trying to abide to a more strict structure could be a way to progress further. Thank you so much for enriching this forum with your truly good movement.
Kind regards,
Daniel–Ømicrón.