Same with the death of Java applets. There were a lot of neat educational Java applets, especially in STEM subjects. Some have been recreated in JavaScript, but a lot are gone.
I remember downloading a VR web pages of a cell and atom in 2000s and hoping to get a magazine CD with a VRML player plugin. It may have been 25MB to download, but it took hours of billable phone time. Seems that dream is lost forever.