1) I think the biggest problem of the song is the fact that there are too many high treble frequencies, so it gets annoying quick.
2) The fakeness of the keys is also an issue, it should be more humanized, varying the velocities and length of each note. But even then, I think all the instruments you chose don't sound real. Which would be fine, but the fact that the song mostly focuses on the keys makes it so that it has to sound realistic imo.
3) like you said, the overall texture is a little stagnant, so I think the instruments have to have enough emotion and realism to pull that style off.
Another thing is that this is more of a remake than a remix. It is too close to the source for it to be a remix. But it is still a good start, keep working on it man!