I think about this sometimes, mostly while listening to In Flames and Soilwork, where it's really clear. It's weird, the less cutting edge mixes tend to age better IMO. A Predators Portrait and Whoracle both aged better than their later work production wise. There are a lot of times I listen to melo-deathy stuff and think "This would be sicker with Predator's Portrait style production". There are some cutting edge albums that came out a couple years back that are really dated already. Fatiguing to listen to and the unpleasant kind of nostalgia.
Any opinions? Certainly not confined to just the bands I mentioned. Talking mostly production, music is entirely a different matter.
I feel like this happens with any kind of production, not just audio. Like you know how there are some awesome looking older movies that have aged pretty well (The Thing, Alien, Jurassic Park) but then the movies that came out in the early days of CG generally look like dogshit (the Star Wars prequels)? Or how there are a ton of SNES games with pixel graphics that still look good but Goldeneye N64 looks comically dated even though it objectively has more advanced graphics?
I mean it's also probably just because metal (especially death metal) went through/is going through a period where brickwalling the fuck out of everything to sound heavier/more intense was/is the norm. Thankfully it seems like bands are starting to either back off that, going for a more traditional sound, or using engineers that have figured out how to get that sound in a way that doesn't feel like someone smacking you in the ears for an hour.