Slackware's package manager is extremely easy to use:
slackpkg upgrade-all upgrades all installed packages slackpkg install-new installs all packages that were added to the repo slackpkg clean-system uninstalls all packages that were removed from the repo
That's not really the point. The point this post is making is that third party software is often not available as a package for your distro. It's been a minute since I used Slackware, but I doubt you can find neatly built tgz slackware packages of Steam or the Nvidia drivers.
I know Slackware has slackbuilds and you can install sbopkg to search for packages and automatically build them, but that goes a bit beyond "just use your package manager".
It's Slackware's approach to dependency resolution. You don't need to resolve dependencies on your system if you just install every package in the repo.
The installed size is under 15 GB, and you get a system that works equally well for a desktop as for a server with lots of app choices out of the box.
(Throwing the kitchen sink at you was the common way to install Linux in the old days, before quick Internet)