Yeah, especially if you play with music disabled, it's really evident that the sounds could be just better. It would add to the immersion and satisfaction if the sounds were more "fleshed out" on the deep and high end.
As far as muffling/lowpass, positional stuff, and echo - unreal hasn't really been outstanding as far as its audio capabilities go. I'm not sure what they have to work with, but depending on the audio library chosen, there might be severe limitations which would take reworks of code to get working, which realistically probably won't happen.
I've noticed the "channel cutoff" stuff as well.
Speaking of sound, I still dislike the design decision to "announce" SC/FP spawns to everyone. Sadly, probably here to stay after all this time.
I've also continued to experience bugs with sounds not stopping. It happens in particular after escaping the "results" screen of a match quickly, right after killing the boss, while some sounds are playing, like the "berserker enraged" ambient sound after successfully parrying with "parry" at 15, the "specimen grabbed you" "shinnng," as well as other similar "looping" sounds. Sometimes, after escape-quit to main menu you can hear specimens finishing their "speeches" as well. Thankfully, most of the time the sounds are "turned off" as the main menu loads, but sometimes a looped sound persists and you have to exit the game and restart it to kill it.
Something probably easy to address is the volume of certain sounds. I think the EDAR sound in particular is just too loud and shrill. Dosh headshot FX "cash register" sound is probably a bit too loud as well.
I said it in my other "huge thread"
here, but again the electric sounds are just kind of... cheesy/bad, in particular the grenade sound and the "EDAR Explode" sound. The fists hard attack is better, although I don't believe anyone can hear those sounds, which is probably ok due to sound chaos, but it might be interesting to try or have as an option. Also, reloading would feel better with metal clunks as weapons open and rounds are inserted.