Chrome probably has the benefit of being updated frequently rather than more of an annual cycle. But Safari still isn't anywhere near IE6 levels of awfulness.
Running a browser on an OS that doesn’t get security updates doesn’t sound like a winning combination.
As much as IE6 was a menace for not keeping up with standards, what made it really bad was crap like ActiveX, radially different layout/rendering behaviors, and shortcomings like inability to render transparency in PNGs and some of the most illegible italic text rendering I’ve ever seen.