I agree with most of what has already been said. The vocal is nice and warm. I also judge a good vocal by closing my eyes and trying to visualize someone singing the lyrics. I can, here.
Agreed that the piano sound, while it has a pretty realistic sound, it's stark sounding. Some might not notice that, but some will. It is a bit overpowering on the left side for a prominent instrument.
The drums are obviously fake and while many people will say "so what?" because they get the job done, I know drummers will listen and quickly get turned off by that fact. I know one drummer in particular who wouldn't even listen to the song because of the drum sound. Maybe look for another sample to use?
Same with what I think is strings, mostly in the right side. They are muffled, in my opinion and need something to bring them out a little bit. I know strings are background, but they don't seem real enough to me. I know they are a midi VST, but like the drums, the idea is to not make them sound as such. The background vocal is fine, but maybe a bit more volume? It's almost not there. I don't know...these are just my opinions. And I'm listening in headphones, so they could be altering some frequencies. Another thing that is just my opinion, maybe a touch more bass volume? I'm nitpicking on most of this and like I said, my headphones could be causing some of what I hear. The mix sounds really good and I think these would make it sound better
What struck me as odd was the step up at 2:14. I think it would sound much better, without the piano chord at 2:14. Maybe silence there, then your vocal starts fine. If you need something in that space, maybe a little drum riff, but the piano sounds awkward to me. I think silence would be fine, before your vocal takes over at the step up with "but, you are great...".
I understand you might have limitations on some of these sounds, but know that my suggestions are minor. The only one very noticeable to me is that piano chord at 2:14.