jQuery was never good at this. When I first used it on a project they had already drooped support for Safari 1.x, despite that being available version of Safari available for Mac OS X 10.4.
I was, at the time, living with my girlfriend and a friend of hers, both of whom used 10.4 and Safari 1.x: it was honestly quite common among people who couldn't quite afford new computers.
Regardless, when we sent the demo of our product for the local school district I was getting reports that the entire browser was crashing, which I traced down to some sketchy code in jQuery that had been tested so poorly on this version of Safari that no one noticed this highly fatal error.
When I reported the issue to a major jQuery contributor (a friend of mine), all I got was flak that people shouldn't be using that browser and should upgrade to 10.5... obviously I have never used jQuery in a project again.
I simply cannot agree with you on this one; in my book, it is not in any way a perfectly sensible decision to make a browser that a ton of people were still using entirely crash when webpages using the library were opened.
The project I was working on was the kind of thing that probably had just a couple hundred people (if that, maybe even less) visit it during our testing period, and I got multiple reports of that crash.
If you want to popup a dialog box on these devices that says "I'm sorry, you are not supported" that's fine, but if it isn't even being on a browser like that, then no: it becomes entirely correct to point out that it was never actually good at handling cross-browser compatibility issues.