You are talking about 30-40 years of lost music… If I understand the OP, he is asking what he missed… rather than list sources to find music, here is the history, from my perspective (I am sure it is quite esoteric and full of holes and some errors):
70’s: Rock: The Beatles were now defunct, Stones continued, Aerosmith flourished, numerous other bands carried the torch of southern rock (e.g., Allman Bros, Lynyrd Skyner), CSN(Y) grew in fame, metal, punk, was around the corner… Springsteen and Dylan grew roots which were strong, art rock (Yes, Genesis, Jethro Tull, Kansas) emerged…
80’s: Rock, Metal, New Wave: Rock lived on, many of the same bands survived (Stones, Aerosmith), many others grew to fame as MTV reared its head… Clash, Smiths, Echo and the Bunnymen, XTC, Elvis Costello, Blondie defined New Wave music, while rock/pop/art-rock continued on… “hair bands” began to divide from metal bands, forming an utterly regrettable and forgettable lineage of frizzy-haired quasi-rockers… Guns and Roses perhaps owned the decade as rockers, Metallica as metal, while REM began to define an underground American college new wave/rock movement.
90’s: “grunge” emerged with some bands growing to fame only to split (Soundgarden, Mudhoney), lose members to death (Alice in Chains), or survive long-term (Pearl Jam, Red Hot Chili Peppers)… hair bands died off, while others grew to define their genres (Metallica, Bon Jovi)… 90’s was somewhat without definitive personality as new pop was prolific in the later half of the decade as the internet changed methods of sharing/promoting/etc.
hope that makes sense… I am interested in others’ perspectives by decade…