If you ruled out the communications aspect, I’d still say the award for most overhyped and underperforming piece of technology would be the Atari Jaguar. That thing was a $250 paperweight.
Nah! That would have to be the Commodore Plus 4... hyped as a "productivity" computer which would include the best C64 word processing, spreadsheet, database, and graphing apps built into its ROM (the "Plus 4" of the name).
When it was finally released instead of four usable productive apps it had a word processor that was limited to 58 lines, the spread sheet was only 16 x 48 cells, a database that was also limited to 48 items and 16 specifics about the item... and the graphing capabilities was only able to draw graphs using a daisy wheel printer!
Can you say "lead balloon?" The inventory was remaindered very quickly to time share resorts who gave away a "computer system" to people who took a tour and listened to the high pressure sales spiel. That's how I got one to add to my collection of Commodore Computers.