I was there and I can say unequivocally that CD-4 worked for me, and I had a pretty low grade system. A JVC 4-DD5, a Pickering XUV-4500Q (the one with the brush) and a Heathkit 4 channel receiver that I built. Of all of the quad LPs I bought at the time (I was in the military mind you), the only real LP's that shined for me and were worthy of demoing were CD-4 LPs and the Ovation Vector 4 QS Demo Disc. And back then, I had a LOT of friends (being in a squadron you automatically had many friends) who came over and they got the big demo. My favorites to use were "Gorilla", "Spinners", "Snowflakes are Dancing", "On the Border", "Machine Head" and "Paranoid".
I do remember making sure I adjusted those little potentiometers on the back of the JVC with the test 45 if I was going to have newbies over that night. Still, I never had huge issues with CD-4, and compared to the shit that was the SQ LP (without a real good decoder [pre-Tate], these were spectacular.
Again, I admit I was an electrical engineer so to speak so I could deal with the extra effort in setting things up that the average housewife/plumber might not have a grip on, but it was not as hard to get good CD-4 as some speak of today. Today, the hardware needed (Demod, Stylus) is all ancient, so it's going to be even harder to get it to shine, but in 1975 it was not a huge deal.
Really
PS - That's not to say they should have had a better approach and unity in the marketing. Same old story. Confused public = shitty sales.