Mastering engineer here. Remastered means that the audio has been modified to fit a different sonic aesthetic.
In general this means made louder, clearer and perhaps bassier, to make it sound "as good" as contemporary albums, as well as optimising it for contemporary consumer sound systems (which nowadays range from 5.1 kits with huge subwoofers, to a mono smartphone speaker).
It's also an excuse to sell the same album again.
I'm not currently able to listen to the examples you've given, but I do believe it to be sometimes detrimental to change the aesthetic of a song and "take it out of it's era", because a cleaner or brighter mix might make it lose a lot of its charm.
It's also worth noting that nowadays, the quality of remasters can vary a lot due to more (potentially less experienced) people using music-making software to create and upload their own.
I'm listening with pretty fancy earphones, I can hear that is sounds more "clear" sometimes, but mostly it seems that stuff gets removed and sounds more flat overall if that makes sense. maybe can you post examples of good remastered songs?
There’s a delicate balance a mastering engineer needs to keep, especially on music recorded a while ago on tape and are considered classics. They need to enhance it but at the same time retain the spirit and soul of the music. That’s why the changes are so subtle you sometimes barely notice anything. I’m sure a capable engineer can make a song recorded in the 60s sound like it was recorded more recently, but then it loses some of its character because how it sounded “old” is what makes it a classic in the first place.
Try the Steven Wilson remasters of King Crimson, and other music he has remastered. A more modern and not so subtle example is Oasis’ remaster of The Masterplan. You’ll notice the orchestral section is fuller, and some intruments that were not really audible in the original are clearer in the remaster.
One that I've been on the fence about liking recently is the Metallica - Master of Puppets remaster that came out about a year ago. I can tell the two are different but it's so difficult to describe.
The one original I don't miss is the CD mix of Rushs Vapor Trails, as that was practically unlistenable and I have no idea who approved it, it clipped like crazy to the point where I was afraid it would damage speakers. Finally remixed in 2013 to a loud (which is fair that's the vibe of it) but listenable mix. I'm glad rush managed to make that happen, one little victory is a great track that was murdered by the mixing.
Sugar Ray is also highly brick walled but I can't tell if that's agressive mixing or just an aesthetic choice to have that kind of distortion and dirtyness in there.
late reply and you probably dont care, but holy shit, I DO GET IT NOW! i bought something from bandcamp simply to support the artist, then i got it as FLAC and jesusfuckingchrist! all those years spotify was stealing like 50% of the music i listen to! switched to apple music and god dammit ... those remasters do sound SO MUCH better, its like discovering everything new! keep the those remasters coming 😍 (but with 24bits pls, i swear i can hear the difference in like 90% of cases, made blind tests and all) the only confusing thing is this spatial audio / dolby atmos stuff. could literally not stop crying when listening to beethovens 9th and dark side of the moon, but the doors were so bad, i cannot even listen to the "normal" versions anymore just listened again and was wrong again, sounds kinda cool, keep those coming too i guess, no idea, but you audio and master engineers are doing gods work, keep it up and all the best 😊👌