I think it's weird to blame Rust for that. I don't want to rush to blame Windows 7, but do consider that Windows 7 is massively EOL (2015; extended support also ended early this year) and I would not fault Mozilla for not doing any testing on that platform anymore. I don't think this has much, or anything, to do with Rust.
Rust is new.. the os software is older than the language itself and eol. Not surprised it wouldn't be tested or supported
Because of that I have less confidence rust will work better or improve my experience. So rewriting everything in rust worries me. It is an anti-selling point.
If a language is living in the now and targeting the future it might not be the best for those living in the past.
It would be unfair to blame rust. But that example doesn't provide confidence that switching from c would be a great idea.