Maybe you're not responsible, but if someone says "something changed in the OS and your previous method is now adding substantial overhead", you could either a) report the change to the OS and mitigate or b) report the change to the OS and ignore the problem for years. It sounds like Mozilla chose b, for whatever reason.

As a software developer, I've had to workaround many many bugs in OSs, especially when dealing with updates to Android. It's just part of the job.

The OS isn't some random third party software, it's one of your dependencies. Your software doesn't work without the OS and if it also doesn't work with the OS, it just plain doesn't work.

That's really not a tenable mindset to be taking these days. With how much Windows has become a constantly-moving target rather than a stable platform, you need to regard it first and foremost as your adversary, whether you are developing against it or are simply an end user. And the days of being able to thoroughly test against every relevant version of the OS are long gone; Microsoft has ensured your QA will be Sisyphean.

At the end of the day, it's about your users.

If your users are on Windows, you have to be where they are. Moving target, wonky API, warts, and all.

Yes, it's Sisyphean. That's why my shop had a whole room stuffed with parallel Windows installs. We couldn't afford to have our users be the first ones to notice Microsoft pulled the rug out from under us again.

You basically just said you stop supporting things once they ship. Doesn’t work properly on Windows? Shrug.

Which is my original point about quality software engineering.. Apparently many don’t test, and if it’s broken, don’t care!