Opera, Safari also have dev tools, although those are both webkit-based, these days. IE's had (non-sucky) dev tools since... IE9? 10? Something like that. I'm sure Edge has dev tools.

Part of the issue with a lot of these alternative web browsers is that they don't have fully-fledged JS engines, or WebGL, or a number of other features that web developers like to use to make their sites fancier (and more bloated, etc etc).