Hmm, I'm not familiar with web-ext. I'm not sure it existed 10 years ago, back when Firefox went through their Quantum transition.
Looks like web-ext came out in 2016: https://blog.mozilla.org/addons/2016/04/29/webextensions-in-.... My extension is at https://github.com/akkartik/spew, and it looks like there might have been a period of a year when I wasn't able to use it.
When software auto-updates and stops working, we consider that breakage. When software auto-updates and code I wrote stops working, we say "oh, it affects just 0.01% of users." For me, the inescapable lesson is to not write code for extension eco-systems, because they're all too immature for serious use. At least as of the year 2015.
