The best thing I can add here is to point the OP (and anyone else who may be interested) towards the forum on renowned mastering engineer Steve Hoffman's site. That is a treasure trove waiting to be found. There's a ton of resource both in terms of the existing (and often lengthy) threads as well as knowledgeable people to be found there. You'll also find regular contributions to the forums from the occasional passing mastering engineer including Steve himself, the legendary Barry Diament, also Dennie Drake and occasionally, Zal Schreiber.
Many of these names may not mean a whole lot, but if you - to use Barry Diament as an example - own a few first edition CDs on the Atlantic label, so pre-remastered we're talking here, check out the booklet, Barry is often credited. He did the first runs of Led Zep discs, some Genesis, and a whole stack of others. Zal Schreiber did ELP's Tarkus album, a brilliant Drifters double disc compilation...the list goes on and on.
In short, the reason why a lot of discs sound rubbish these days is depresseingly because some producers and labels think we want it LOUD man. The reality is these guys I mention know more about dynamic range and fidelity to the recording in their little fingers than a whole bunch of the current crop will manage in their entire combined careers.
If you want an example to try out, get a hold of the latest Genesis remaster for A Trick of the Tail. Then get a hold of a first edition disc. I favour the US Atco version (either the one made in the US or the one made for the US Market in Japan - cat. no. is US Atco 38101-2) and compare. The 2007 remaster/remix is a botch job. Crushed by compression in a way the original disc isn't. Drums way too loud, cymbals ear splittingly sharp - awful. The Atco on the other hand was a revelation (ho ho, genesis to revelation...see what I did there?), a huge soundstage, depth, instruments sound real, there is colour and texture to the music.
Nick Davis (who did the 2007 remaster) (and is a good guy - see his work with XTC in the 90s for one thing) was pilloried for these. My gut feeling is the band had too big a hand on the tiller. Whatever. It's a fine example of how to get it right (and oh so wrong).