Today 10 years ago I went to Poland to buy a Phone with pre installed #Firefox OS on. The Phone was a Alcatel One, so very shitty. Two years later I installed Firefox OS on my Nexus 5 instead https://jeena.net/photos/111
It was a very good concept, but sadly rolled out on too shitty hardware so it never caught on.
This was exactly my (dumb, layman) view of things - great idea hobbled from the outset by the marriage of slow web apps with slower hardware.