Hi there, i'm gonna give you some feedback.
First of all, nice build. I like the vibe of it, and it definitely has potential, though I have some suggestions for it. I think that the trees can do with being manually made (I know, that sounds tedious) but the thing is, if you manually design and shape a tree you can make it look very customized and attractive compared to the generic minecraft tree that weve seen thousands of times. It doesn't even have to be fully random either. You could build a few stems and then use w/e brushes to build the leaves, then copy and paste the few trees you've designed around the island.
A small detail like this will help a lot. As well as this, though right now it may be too late, in the future, it is important to hide traces of worldedit. In this case, the massive rock formation looks obviously made up of a sphere brush, which makes it look unnatural. To fix this, you can try to manually smooth out the bumps or use a //brush blend. You can also add a bit of details to it through //brush erode.
I unfortunately can't do the parkour so I can't speak about it, but I think that you do have a lot of potential here, and this map can be really good with a few improvements. I wish you the best of luck.