I'm trying to think of examples of technologies that were innovative and basically worked, but weren't potent enough to overcome the skepticism eventually, and/or couldn't overcome the deadweight of externalities. 

Not potent enough: flying cars
Couldn't overcome externalities: nuclear rockets

Any others?

Delver at contraptions.venkateshrao.com, running summerofprotocols.com, host of /gloom ☀️

This is a good example to think about. It demonstrated a lot of features that eventually made it into Slack, Discord, messengers, and even Gmail, but the Wave model itself I agree worked but was not potent enough to be worth it. I remember being kinda excited by it but then meh about it a little later.

Same could be said generically for most shuttered google products.