Alright, I played around with the stems for a bit. I have a few general suggestions which may help in this particular use-case-
1. It's best to avoid mixing instruments of different amounts of baked reverb/room into the same group, instead separate out instruments of abnormal wetness/dryness to their layer into their own groups (the super-close mic'd solo trumpet vs. the percussion, the overly wet upper strings vs. the super dry bass, the damp flute vs. the dry piano).
2. That snare is really low-mid-full. I would cut out most of the mids and boost the highs a ton on it so it has that 'sizzle' or otherwise find a different snare. It's also kind of 'damp' and very centered, so it really hates any and all reverb with a passion...
3. In general, percussive sounds can 'take' less reverb than sustaining sounds. Strings and woodwinds can soak up tons of reverb and sound great, but a little too much on a snare and it sounds like a dish disposal eating a wooden spoon.
4. The best samples for adjusting are recorded neither close nor far but at a comfortable distance.
Basically I just made an eq which looks like a big crater and tossed a ~3s concert hall convo reverb on the output, then a bit of compression and an exciter to get a little more sizzle.
Even with that, I didn't have much more luck than you to be honest. It's very tricky to combine these sounds well, it really needs to be mixed per-sound, possibly with some processing of the samples beforehand to try to mitigate the baked reverb. It's sort of like having a bucket of wet cement with chunks of dry in it then pouring water on it, versus a bucket of dry cement and pouring water on that. One bucket is going to be a sloppy mess no matter what you do with it until you manage to get it dry enough to work with and those pockets of dry cement are going to cause problems unless you break them down and mix them in proper, the other is going to be good to go so long as you don't under or over add the water. If you already have your bucket already a little wet all throughout and you just add a tiny bit more to get it to the right consistency, that's ideal.
https://instaud.io/1U7t
Here's a piece I remembered I did years ago using a bunch of free soundfonts. Each instrument had at least one EQ and faux stereo effect on it just to get them to work in the space and I had to do a lot of digging just to find sounds that would mesh right. It's still a bit of a mess after all that-
https://www.newgrounds.com/audio/listen/568889
The kind of sound which is most flexible is a mid-range stereo recording, with little room, but far enough from the instrument to make the proximity effect negligible (about 3-8 feet, depending on the space)-
https://instaud.io/private/33ccfb6d53080...4a8709155e
Now I will magically transport the viola onto the stage, as if we were listening from omni mics at about 10 feet-
https://instaud.io/private/628b7384c68a7...89a10a9031
Now we will go back to off the edge of the stage-
https://instaud.io/private/3b112d7e4e303...6195b46c98
(I applied a little stereo thinning to about 50% and stereo pan slightly left to the concert position of the viola, then attenuated the highs and lows a little, then put on some convolution reverb)
It's important to keep in mind when using algo reverb rather than convolution that in a convolution is a "baked sense" of the absorption and diffusion of the space, something which must be modeled in an algo. Absorption depends on the materials in the space and their exact location. Although it may not be noticeable, moving a single baffle on a stage does adjust the acoustics of the space. Typically absorption eats up your high frequencies, but if you're recording with cardioids, you will lose quite a bit of lows as well. Besides, cleaning out some of the mids (250-750) is almost always a good idea before sending something into reverb, as that is where mud often is the nastiest (although low mud as well is not nice). That is a bit of what I have simulated here. By recording far enough away, I managed to avoid the proximity effect and the undeveloped tone of the instrument, but not so far that the existing ambiance would make it difficult for me to change the space. Rather, as you can hear (and are welcome to try for yourself on the original dry track), it takes to the reverb very nicely and is easy to move around between spaces. I can even put it in a different sounding studio if I wanted to-
https://instaud.io/private/4efa179b34082...8a98bdcace
Edit #5000: In short, when 'shopping' for samples, look for things which when dry resemble that, so that you can move them and work with them as easy as possible.