Could be.
Or....the white garage, or the mostly whitish soil?
The almost too large pot? Oh no, box, that is better.
It could be any or all of these thing.
Hell, could even be the tree just needs to cast a little more shade, fill out!
Hell with it. Again for me, lean the rock and all about 30degrees forward in the first pic.
It holds the rock too nice to change, so I'd just grow it out. If it still is unconvincing then, maybe it'll be an easier fix.
Two questions.
How long has it been on the rock?
How much do you have into it?
Sorce