It's taken me a while to get to this (So I apologize) but a promise is a promise! I've also noticed that this piece is a loop, so near the end, I'll evaluate it as a loop (Like, does it loop well, etc). With that said, let's start with your instrument choice.
The piano sounds really good. I'm liking it. The drums also sound good and aren't too cheesy sounding. I'm not sure if your arp at around 0:17 is playing at the same frequencies as the piano. If that's the case, then that would explain why the piano kinda gets drowned out. You could try ducking one sound under the other sound or change instruments entirely. If however, the arp at 0:17 ISN'T playing at the same frequencies as the piano, then it seems like it benefits from playing in some frequencies that you weren't using too much and so then it would be a good choice of instrument. If you still have the project file, check the frequencies your piano and arp are playing at. Your music box sound at 0:25 was a great choice. The rest of your 'ambiance' in the piece, created by the other sounds, sound great too. All in all, despite the arp I mentioned, there's no real complaints here. Good!
Composition-wise, I'm sure you've heard it before. It's a little too repetitive. But, contrary to what others seem to be saying, it's not a huge detriment (It's still a flaw though). The song isn't a complete experience, it's a loop. Loops, in my opinion, are almost always a little repetitive. That's just how they are. One's enjoyment of the loop then comes from how much you enjoy the repeating motif, as opposed to a song, where one's enjoyment comes from their feelings of the entire experience the song creates. That being said, I enjoy the piece from a composition standpoint although it is a little to repetitive for a loop. If the loop wasn't 2 minutes, I'd have no complaints. but, due to its length and repetition, its not as good as it could be. I would've enjoyed it if the song ended around the 1:10 mark, since it already seems to be simplifying down to what the piece started with.
For your mixing/sound levels, the piano gets drowned out. This is really my only complaint. The piano struggles to be heard over everything else. That could be a volume problem, or some other instrument is taking up its frequencies. Everything else can be heard nicely - which is all I care about with mixing and sound levels.
There's very little theme to touch on since loops aren't fleshed out experiences. The feel the loop creates is consistent throughout the piece so that's good. Not much else to really say here.
Overall the loop is good. But not great. If the loop was shorter, then the repetition wouldn't be a huge issue. The piano either gets bullied by the other instruments for frequency space - which causes it to be too quiet, or it gets bullied by the other instruments for dB space - which causes it to be muffled. Those are really my only issues with this piece. These problems are what I find holds the piece back from being pretty good. But it's still good as is!
Cheers,
-Yeelp