for a one man job and at the age of 18 I think you are going off at a good start.
sure it has lots of its flaws and inconsistency but it brings me back at my age when I also started out animation and everything just works.
but as you progress and get better, its gonna be much harder to pull off a epic 15min animation by yourself when you want every scene to be at its best quality. ;)
take the critics that review your work with some thought. you are going somewhere with this and keep at it.
I've not much to critic as most of the critics have already pointed out the flaws and I would be repeating myself, so heres my encouragement post and keep carrying on your passion to your craft.