Has the flame finally gone out?

I agree and feel deeply that this damaged made to "the times" is more directly to blame on the industry itself. In the U.S. during the late 70's, Americans loved Prog. The industry took it away and people's attitudes changed about music because they were being sold something else that changed that attitude to respect musicianship. This entire business decision to shorten the length of songs influenced the minds and mentalities of younger generations that began in the 80's and extended through the 90's. People in general began to develop a short attention span for music ...as a result..over time of 3 decades. In the 70's the young audiences to see Prog bands play live varied in music tastes. NOTHING was compartmentalized into any business concept or any worry of a cult following instead of a massive one.. or that the music would fade and finally die. 

Originally "Progressive Rock" appealed to masses and it had the finest respect from audiences for it's musicianship. I can't believe that it was actually represented over a period of 5 to 6 years ..as something to be taken seriously. No doubt, you had to be there..in the 70's.. to appreciate the surroundings of it's social gatherings and the seriousness of the music. Often it is said..."yeah..but..that was then, this is now" and to be honest what difference does it make when people my age are under the impression that there's something missing from the music. So...in point...maybe what you don't hear is something that was erased by the industry by their business motives to change music and the impression that would have on people. An impossible theory to back up with precise evidence...however...the simple idea to change music by replacing what was there in 78' with a new fad in 1980 could have influenced a mass of people to think and breath music differently than you or I. Which is the answer as to why the average person has a short attention span to a piece of music that contains more than 4 chords and 10 notes. On the average I would say that this occurred 40 percent of the time in the 70's. Even people who were afraid of ELP's music desired to investigate it. Everything was extreme and sometimes it felt like music as an ambition in life, was about being progressive.  

ELP's last album was crap but then they were virtually crippled and trying to churn out an album to save a dying record company ( they might just as well as bombed it for the good it did). Their last brilliant album anyway was 1973's Brain Salad Surgery

Yes - Relayer was the last time they made a significant progressive rock statement imo although there are plenty of good albums that followed and I do like the most recent.

Genesis and the descent into pop music has been discussed to death but then they stopped being a proper working band 20 years ago.

Jethro Tull is the one band of the big five I don't own much of. I'm guessing though that they haven't made anything as good as say Thick and A Brick or A Passion Play since those albums. They found massive success in the USA in the eighties although I gather a lot of it was not proggy . The recent stuff by ian Anderson I do own and its very good but not exactly earth shattering.

Other than KC the big five were on slippery slope from about 1975 onwards. King Crimson has bucked the trend by to all intents and purposes being an ongoing project of Robert Fripp rather than a band in any traditional way. A band has to have an ongoing collaboration of a core membership. King Criimson barely had that at all. Fripp decides what he wanted to to do and then recruites accordingly. Nothing wrong with that and avoids the possibility of lurching head first into self parody which often happens to bands that have been around for thousand of years.