You know my take on this, but I'll get this thread started. You have a beautiful melody, and this will be the star of your piece There are two thoughts here. If your harmony is simple functional, and you mainly stay in key, you HAVE to have a good structure and melody. If your piece is not melodic, than harmony becomes a lot more important. The main issues I see with this piece:
Your solos come out of nowhere, and make your piece sound unfinished, and lonely.
Your ending was much better in the version you send me over Discord, what happened to that? Your ending here sounds very drawn out and unfinished.
At 6:14, you have an odd key change. The problem with something like this, is that you mainly stick in key throughout, and you already set expectations for your audience (simple functional harmony).
I would reupload your newest version for better feedback though!