> These days, I'm more likely to suggest Brave over FF, if someone really requires a Chrome alternative.

Brave is just a reskinned Chrome.

> We [web developers] owe a lot to FF, Firebug, etc, but the writings on the wall for mobile and desktop.

Where I work developers have mostly switched to Firefox over the last few years. Firefox is just a better browser (faster, less bloated) under the hood. Yes, Firefox will have a difficult time sine they don't have their own proprietary walled-garden ecosystem as a distribution channel, but the technical product is solid.