It's actually the opposite situation. Slackware's policy is to stick to the original software as distributed by the author with only minimal patching where necessary, so if a particular program (say, KDE) has a big support community, Slackware benefits from all those eyes on the code. This leads to a very mature and stable system at the expense of running older versions of software (though there's always the -current branch for those wishing to live on the edge).
Beyond this, the small but dedicated Slackware team is working daily to find and patch bugs when they do appear. You can look at the changelogs for examples of that workflow[1].
There's no such thing as a software project without bugs, but Slackware is consistently one of the most stable and robust OSes out there.
