When you stopped buying their albums...

Genesis: Duke.. Abacab is too much

Yes: Drama  90125 isn't Yes, but then I oddly loved Talk and Magnification isn't bad either

Camel: Rain Dances.. Breathless is too much of a divergence, but Rajaz was very good

Pink Floyd: The Wall, although Division Bell is pretty good

ELP: Brain Salad Surgery, and that was a stretch for me

BJH: XII.. a notable change after Wooly left

Hawkwind: Simply too complicated to answer... the subject of a doctorial thesis..

Moody Blues: Obviously Seventh Sojourn... everything after (more or less) is total pap..

Mike Oldfield: Very hit and miss after Incantations, still exploring much of it

Kansas: The first Five and that's it to be honest

Rush: They didn't lose me until Vapour Trails, which along with Snakes, I never could get into

Eloy: Oddly, I know the answer should be Performance, but there isn't an album I don't enjoy, even the much derided Ra. Go figure.

I hope that's been helpful, thanks for the question...

ELP - In The Hot Seat

Yes - Magnification

King Crimson - The Power To Believe

Jethro Tull - Crest Of A Knave

Genesis - Invisible Touch

Pink Floyd - Pulse

Genesis: ATTW3

Crimson: Discipline, though I have a few after that

Tull: Stormwatch (got RTB... and Crest after a couple of decades after release)

Floyd: never stopped buying (though I wish I hadn't AMLOR)

Yes: Tormato/Drama (and the two KTA afterwards)

Tangerine Dream: Force Majeure (Green desert is the only one since)

Caravan: Blind Dog

Rush: Pictures

Camel: Moonmadness

I wasn't into Soft Machine, GG & VdGG back in the 70's 

.

What I can tell is that in 1978 my music interest started to turn away from progressive music.

Let's see ...

ELP - bought Karn Evil ... that was that for me!

Genesis - A Trick of the Tail

Jethro Tull - Minstrel in the Gallery (it was all pop songs after that!)

King Crimson - when BB left

Pink Floyd - Momentary Lapse of Repetition

But mostly, for me, it was that the bands had lost their way ... I bought PF and even today, the material I enjoy the most is the earlier stuff, even going back to Syd, and though I bought Roger's stuff, it simply was not as uplifting and fun stuff. Also, sad that Nick Mason had no more fictitious adventures to his solo career as that one was magnificent fun!

YES was sad ... a bit before Chris passed away I caught them here at the Indian Casino in Oregon, and it was the saddest thing I have ever seen, and even all the women dressed up in late 60's fake costumes and make-up just made the whole thing gaudy and a bad Fellini movie, not to mention a singer that did not know what the lyrics meant and was using stock hand expressions that are thousands of years old ... it was, literally, pathetic, not to mention that many folks in the audience only wanted to hear CTTE and Roundabout. Totally pathetic, as if the band was just another top ten idiocy.

JT, I have never bothered to see, especially after he "quit" on PP and while I liked MIAG, it did not feel complete, and I think that he did not like the fact that those last 2 albums did not sell gazillions, and right after that he was all over FM radio with pop songs ... nothing but!

ELP I liked and would have bought more but after hearing the fiasco and the audiences laughing (one bootleg even had them booing the orchestra), I did not want to hurt the feeling I had for everything to KE9. 

Genesis, I would not bother to see after PG left.

But some, never die ... Tangerine Dream and Klaus Schulze were good to the last drop! And that is something that these "top goons" did not accomplish even though they are considered by folks that don't listen to anything else the top five ... only one of them is in my top 5. The other 4 are respected by me, but there is better music out there in the world that we refuse to accept as a better top 5 group that at least 2 or 3 of those. I would never select JT before Banco del Muttuo Soccorso, for example. 

KC is another discussion, and while the appreciation is there and I saw them some 3 or 4 years ago with the 3 drummers, the musicianship is the best I have ever seen on any band, although I have not bought anything since BB left, except one of the live albums of the recent shows.

ha! I said exactly the same! There was a perceptible move toward commercialism afterwards, wasn't there?

Genesis - Duke

Yes - 90125

JT, KC, and PF I have everything they made (studio album wise) (and will probably buy more if they make more).