A lot of things that have succeeded today were tried then and failed either because the technology couldn't scale, or the bandwidth wasn't there, or because people just weren't ready for it.
Failure reasons were the ones you list plus lack of TCP/IP provision.
I was on the internet in the early/mid 90s, and was told that "the web" was growing massively and was going to be huge. This was more common knowledge by 1997.
The kind of DNA sequencing that 23andme sells to people for £150 now? It's not "millions of units" massive yet, granted.
Minor nitpicking: the 23andMe kits use microarrays for genotyping, not DNA sequencing. It's an older and more limited technology but it is much cheaper than sequencing.
The infrastructure and technology was not quite there 20 years ago, but we are getting close with today's cloud and webapps
What was 20 years ahead of its time then? What would you have looked at and thought "That'll be massive in 20 years"?
About the only thing I can think of is VR. Which Sega tried to launch in the late 90s, and only now is selling over a million units.