As stable or user friendly fedora and debian are, their whole structure due to the way they setup their ecosystem including their package management differ in how to change things system wide as you dont want to go too heavy on it to avoid breaking, especially if you tinker things to where you conflict with its package manegment. Aka your configs vs apts/dnf package managers configs, at some point a conflict will occur to where you will need to fix it.

Slackware lack of package managers creates the initial issue of well now i got to manually take care of the dependencies. However in exchange, the packages are close to the way they were initially developed and your config system wide has significant less competition on what happens to your configs systemwide.

You can make your debian or fedora your system, however slackware gives you that initial power out of the box hence its superb stability + even if i make a mistake i find slackware to be more forgiving to fix the issue.