Horizon Linear Redesign

I’ve been working on this for far too long and I think it’s time to take a step back for a while and work on a new piece.

I want to add more, particularly make the ambience more lush and lively.
I feel like overall it sounds kinda flat and I’m curious if anyone can provide any insight into how I can fix that. I’m not sure if it’s my sound design, my mix, or maybe both?

I really appreciate the tips and tricks you all have shared with me so far!