I would say albums as an art form overall. Yes of course some bands and musicians will still write an album in this way, but music has been playlist-ified to the point where most people won't listen to it like that. You take a song or two from it and forget the rest exist. My perception is that it's been a dying thing for some time now.
I also pick off my favourite songs from most albums, to be fair. But there are some albums that are best viewed as a single piece of art and I feel like that understanding from both listeners and artists is dying. If you just listen to Money and Breathe (In the Air) when they show up in your shuffle, are you really listening to Dark Side of the Moon?
And discussing with your friends which side is better. I listened to dark side of the moon and Sgt pepper and aerosmith greatest hits and a dozen other cassettes so many times!! Then when you hear a song on the radio you expect to hear the next song follow it.
I've been listening to the 1001 albums you have to listen to before you die list. (There's a website that randomizes it and gives you an album a day).
I'm about 100 albums in. The grand majority are trash, that includes stuff by the Beatles or the Rolling Stones or Janis Joplin, etc. Just absolute garbage. One of two songs worth listening to and the rest is straight trash.
Albums as an art form died because it was never really a good art form to begin with.
Mix tapes all the way! Sometimes even recording straight from radio shows praying the host wouldn't speak during my recording.
The only album I bought in an original cassette was "August and everything after" by the Counting Crows. I played that tape every single morning going to school for like a year.