>>11980621 (OP)
Stopped making money. Myst was a big money maker, it was the cutting-edge tech demo of its time, that's why it got so many rip-offs. Most rip-offs just copied the trippy aesthetics while offering weaker puzzles and worse atmosphere, so the genre became associated with boring slideshow shovelware. The jump to 3D only made them more awkward. Once the novelty wore off, many players found it dull, got stuck on opaque puzzles, or tired of pushing random levers. When immersive 3D worlds with combat, platforming, and variety became the norm, Myst-likes games lost their broad appeal and survived mainly among hardcore puzzle fans. Or had to adopt different theming, like horror or detective games.
Point-and-clicks, puzzle adventures, and escape-room-style games still exist, especially on Steam and mobile (stuff like The Room), and all of them owe a big debt to Myst. Flash era was another turning point because of the low barrier to entry and free accessibility, it really popularized escape-rooms but made it a cheap genre.
Cyan is still around: they recently put out the Riven remake and added a new island to their Myst remake, though they are struggling financially and lost their spark a long time ago. Amerzone also just got a remake.
There are plenty of indies carrying the torch. Some are more direct Myst homages, like Quern or Neyyah. Or reinterpret the formula in more original ways: Outer Wilds, The Witness, Blue Prince, Platonic, La-Mulana. All of them excellent Riven spiritual successors.
Coming out in a few days
https://store.steampowered.com/app/1289720/Neyyah/