Your parent is referring to the long time period before Firefox really took off that IE6 was Microsoft's best offering, and we've all heard how terrible it was ad nauseum. Even once FF took off, it took them years, until IE9 in fact, to release a browser that could be considered semi-modern and standards compliant, and it still is missing a number of important features, and isn't even available on Windows XP.

That IE is no longer rotting is certainly true, but that's only because of the competitive pressure from FF (and now Chrome and Safari as well, of course.)