Hello sir!
I have had the pleasure of listening to your work. I do not think of myself as an authority enough to comment anyone properly, but I'll do my best...
This piece of yours is (to me, at least) reminiscent of the pre-baroque choral music. It is based entirely on single key, with the exception of the subdominant's dominant (that is, the diminished subtonic) in that rising sequence, which is, also due to the melodic lines of the voices, very much giving that modal feel to the piece. Looking at the instrumentation as well, I guess that was your idea all along - in which case, congrats, you made it!
Only one thing captured my attention as being slightly awkward: the ending itself, that long timpani tremolo. In my opinion, you should end with a corona on tonic, since timpani tremolos in that manner are usually a way of ending large-scale work, mostly in XIX century romantic style. When those are presented here, it gives a slight feeling of the end being "bigger" than the rest of the piece. Also, judging by the pieces I listened to (and some that I wrote), it is common to use the following formula when writing such endings: those two short chords atop of the tremolo (bars 116, 118) are usually 6/4 tonic chords (in your case - d-g-h), because the tonic that rests on the dominant (as is the case in this chord) sounds unstable, and gives the feel of the need for resolution, which is then, later, achieved through the use of the tonic that lacks the third (in your case - g-d-g) an octave below the previous two chords (in your case: d-g-h, d-g-h, g(below the dominant d in the previous chord)-d-g), because the use of the chord that lacks the third (that is, only has tonic and fifth) in the low registry really gives that "grounding" feel after which there is nothing else left to say. I hope I didn't write too much
Hmmm, I think you are being too rough on yourself. There are no "problems" here... I mean, no one would judge your piece compared to something not of it's genre. Given the fact this your firstborn, and that it is, I believe, meant to sound archaic, there is no problem whatsoever. You have well captured the holiday spirit in the sound that is similar to the old sound of choral music.
However, this is the first step, meaning, there should be a second one, as well. So, move on. Challenge yourself with something more difficult, experiment. My theory is that a composer doesn't need to like all music, but needs to try all music. I have a friend whose time stopped in 1791. with the death of Mozart, and who denies almost everything that appeared afterwards. Don't be like that.