Without getting too much into composition...
Beautiful footage. However, the digital artifacts are off the charts...completely unwatchable in my humble opinion.
Looks like you may have rendered in Adobe Premiere Pro. Re-render using "YouTube" settings. It's counter-intuitive, but these settings will net the least artifacts in the YouTube space.
Check out this "action" video (shot in 4K). Originally, it was littered with digital artifacts. Here's a 1080p rendering, which shows SOME artifacts, but not nearly as bad as my original renderings, which were on par with your video. This version was rendered @1080p, which nets SOME artifacts. Watch it full screen to see the same sky/tree artifacts your video is afflicted with.
You'll noticed digital artifacts throughout the above video. I tried a half-dozen different render settings before discovering the "YouTube" settings. I usually use h.264 "High-Quality" settings for my Canon footage. But the highly-compressed, low-bitrate GoPro video just choked on it. So for grins I opted for the h.264 / YouTube 2160p 4K settings and wella...artifacts gone (well...most of them).
Here are the export settings in Adobe Premiere Pro.
View attachment 117143
Hope this was the kind of constructive criticism you were looking for. By far, re-rendering with the correct settings will net the single most profound improvement in your video of any advice you receive via this forum.
Good luck!
D