Okay, "Tis So Sweet" it is... bear in mind then that the following is my personal critique driven largely by my own tastes and only reflect how I would have arranged differently. Please feel free to disregard, ignore, or do-the-opposite of any of these points

Also, feel free to chuckle at my terminology - my musical training is extremely limited so I'll likely be describing things incorrectly.
First off, my own personal preference would lean towards minimalism, especially if piano is your primary instrument and, in my opinion, the genre tends towards the spiritual/reflective as in a hymn. So let's walk through your rendition (with timecodes):
- 00:00-00:39: nice introduction. Are you doing something here to quantize (or note-align)? Seems a bit too perfect and could use a bit of human spacing. Also, the strings are matching the piano chord progression a little too closely. I would have stated the theme via solo piano first, then bring in strings for restatement, but with string progression maybe 1/2 that of the theme (i.e. if piano is quarter-notes then string chord progression at half-notes).
- 00:40-00:50: I would cut the mostly-solo drum intro by half.
- 00:50-01:11: nice. I would drop drum volume by maybe 30% and toy with a little less "filly" drum line just for comparisons sake.
- 01:11-01:30: cello(?) line with piano is nice but again too closely mirrors piano. Maybe as little as holding the occasional cello note over 2-3 piano notes would create a bit more space? Also, cello attack a little too punchy (probably because you need the attack to mirror the piano?). By spacing out the cello maybe you'd be able to lower the attack and get a more natural sound?
- 01:30-01:52: down to drums, strings and cello. Same issue with punchiness of strings mirroring cello. Ideas: pad in back? / maybe very soft refrain of opining piano line in back?
- 01:52-01:55: down to cymbal and then some kind of "break down" sound effect filler. I'd probably drop, if for nothing else than in my opinion you're only allowed one "drum introduction solo" per song. I think it's a law somewhere

- 01:55-02:36: other than dropping drum volume I like this section. Piano work sounds natural and fills in around the drums and other instruments.
- 02:36-03:22: mostly refrain, now with synth(?) and some new drum patterns. My sense is that by this point you're committed to your instruments and drum pattern, so adding more here seems like too much. I'd drop this whole section and go straight to the next.
- 03:22-03:42: I really like this much more natural, spaced out string here, which doesn't feel like it's mirroring anything and has it's own breathing space (well, there's a couple of points where it switches to plucking, which I'd drop).
- 03:42-04:02: still solid with the string here, but you change up the drum line a couple of times. Same comment as point #8 above.
- 04:02-END: back to jazz piano and some final refrains of theme. I would consider scaling things back for the final refrain or two, maybe back to something eventually resolving to the opening piano line?
For something like a hymn, I would consider maybe starting with a full play-through on solo piano, and then layering strings and drums on top? You could always drop whole sections of the piano out if you wanted to change it up and emphasize the other instruments, but maybe that standalone piano line would ground the piece thematically and help steer your arrangement decisions?
Take, for example, Jacqueline Schwab's piano work here:
And imagine as you listen to this where strings and maybe bass or drums (e.g. almost just a metronomic rim-knock) could fill this in to give a bit more depth.
Anyway, I hope maybe in all of this there's an idea or two - like I said I grew up playing and taking enough stabs at arrangement to realize that much of the magic is in the arrangement. You've produced a complex and multi-styled piece that God knows I'd never be able to play. All I think you need to do now is figure out how to scale it back to a more simple, primal core.
Good luck Caleb and let me know if you produce a new version!