FireFox constantly broke all my extensions with just about every minor update. It was maddening. After being a die-hard FireFox/Netscape/Mozilla user since the 90's, I finally gave up a few years back and switched to Chrome. I can't recall a single time since then when my browser or extensions stopped working because of any update, not just a minor one.
They broke compatibility with v57 exactly for that: to make continuous small changes. The previous situation was untenable since there was no API for extensions, the extensions could just go through Firefox internals and change at-will whatever they wanted.
The whole point of WebExtensions is that they won't need to break compatibility after this huge leap.