Not really hearing the piano as 12! But it's a tad hard to determine against the synth. Lovely atmosphere anyway, and great pacing of said piano part.

The cello, however, feels rather meandering and mostly just drones on. I'd love for it to have some lines with more of a direction.

Pretty nice overall! You use the tremolos to good effect, and the runs up and down in register are well executed. It's nice to hear someone using brass in lower dynamics.

These are the things I reflected about (more or less in some order of importance):

This is somewhat subjective, but I feel that for a large part of the track, you could use something that glues the orchestration together more. The staccatos, while they provide the drive and rhythmic motor, are pretty naked in themselves. In the first part up to the trombone solo, the highest tremolo covers this role nicely but during the solo, especially since the melody is somewhat jumpy, a bit of glue would be nice - some suggestions, if you want to vary the texture, could be high woodwinds (doubled with strings or not), low woodwinds (bass clarinet would be very discreet) or low brass (though this would be more likely to conflict with the solo role of the trombone). During the classical period, horns and/or bassoons often filled this role, as well as the higher woodwinds. Since you mentioned it in the description - I think you could definitely use the brass to fill things out more, if you want.

I'd watch out with the intervals in the low strings, intervals smaller than a fifth usually sound very muddled in the low registers. In the intro, the last interval (a fourth? bit hard to hear down there) between what I assume is vlc and cb sticks out rather sorely.

One rather boring critique is that the trombone sounds rather synthy when it has the solo - when the brass are combined later, it's easier to accept things as realistic-sounding as there's more stuff going on. It sounds like you did a decent job sequencing it, but it is so very naked in the solo that the patches weaknesses are very exposed - relating to the first point, adding some orchestral "glue" might help things! The trumpet also seems to be very high in register for how soft it sounds - trumpets in the highest register will usually be pretty loud, just one thing to consider when doing midi orchestration since it is after all a recreation of the real deal.

One critique about the composition that I have is that the ending felt rather unjustified - there's no build-up to speak of, nothing that intensifies, so the little trumpet explosion feels pretty silly and out-of-place.

I kinda wanted a stronger bass most of the time, and during the trombone solo, the trombone felt rather loud compared to the strings, but otherwise the mix sounded pretty good.

That's all I could think of right now!

Nice, I really dig the chord progression. The drums, and later the lead, feels overly loud compared to the rest of the track though. A more drastic contrast somewhere in the track would've been nice as well!