Despite its longevity, Slackware has limited appeal. The distro is ideal for purists who don’t need the conveniences offered by other modern Linux distros. It’ll suit those who can appreciate its approach of not anticipating use cases or precluding user decisions. However, if the CLI gives you cold feet, you’ll find Slackware has a dauntingly steep learning curve.
The other distros are a lot more welcoming. Debian pitches itself to desktop users, developers and even for enterprise use cases because of its focus on stability. That said, Debian’s freesoftware-only approach limits its appeal for pragmatic desktop users looking for an install-and-use desktop.