I don't blame anyone if they don't want to support Edge/IE. Microsoft's browsers are horrible to develop for. Personally I'd be much happier if more of my users would switch to Chrome.
I haven't tried to write extensions for Edge or anything like that, but have you recently developed for Edge or even IE11? I've run into a few minor warts (minor as in a 5-minutes fix) with IE11, but it's been smooth sailing with Edge. Mobile FireFox has comparatively been a nightmare in spite of MDN's wonderful docs.
Having been a FF/NS/Mozilla browser user since the 90s, I know it's not nice to be treated like a 2nd class citizen. However, unlike the current Edge/IE users, I made a choice.
