I have mixed feelings about SACD. I can be far better than standard cds, but only if they are recorded well and mastered right. I have several SACDs that sound no better than CD, mostly because of lousy recording. Engineers get thrilled by the sense of space and record in highly reverberant settings, and the sound just sucks.
But if a great recording is made, the sound can be thrilling in SACD. I've demonstrated to people several times using the Paray recording of Symphonie Fantastique on Mercury using both the cd and sacd versions. Once you get them synced accurately (no small task), then rapidly switching between players reveals startling differences in detal. With speakers the differences are less noticeable because of ambient sound, etc. But with headphones (I use Senn 650s) it's amazing. There's so much more life in some of those older recordings made my Mercury, RCA and a few others. Pentatone is remastering many older recordings in sacd and the improvement in sound can be tremendous.
Having said that, there are other things. First, for most people, sacd offers no improvement. Metal, Rock, Country probably don't improve noticeably. It takes more subtle, detailed music to really benefit. That's why sacd has survived in the classical area. Then, when most younger people listen today with mp3 ear buds stuck in their heads, they have no idea what true hi-fi can bring to music -- and they don't care. The lower quality is ok to them.
SACD will eventually go away, sorry to say. The primary reason is the greed of the industry. They needed to make reliable, good sounding sacd players available for under $100. But they didn't and the public didn't hear the value added as being worth the huge prices that Sony, Denon and others charged. I just bought a new sacd player from Oppodigital, and it's great, but not being a mass market product, it's too little too late.
This Oppo player also plays HDCD. I have several dozen disks in that format, but never had a player, and I have been stunned to hear just how great HDCD sounds. In fact, those recordings for the most part sound better than the sacds I have. The impact of sound, the presence and the bass are thrilling. Of course, the recording processes have a lot to do with it.