There was nothing wrong with IE6 when it released, the problem was the fact that IE was too integrated into Windows that it required an OS update to upgrade the version. Had it just been a standalone application like Firefox there would never have been so much rage and hatred over one exploit after another for IE.
Browser updates were slow back then, even for Netscape, so this didn't matter at all.[1]
I have never once heard anyone complain that the reason why IE6 was bad was because of "slow updates because it was part of Windows". It was bad for many other reasons, but not that. Microsoft released plenty of hotfixes outside of the normal Patch Tuesday cadence.