I've been using Linux exclusively since the mid 90s. I've run so many different variants. I was a attended the church of Slackware for a long time. There has never been a time in my many years of using Linux that anything has been "flawless" and I _definitely_ have to install things "outside the repositories" pretty regularly. Even if that's a broad statement meaning "any type of repository anywhere, including but not limited to git."

Right, I'm struggling to think of a user profile that would be OK with just software from major distro repos.

"Normal" users? They're going to want several proprietary programs, some of which will surely not be in even the non-free repos, unless they're an only-uses-the-browser type who'd be fine with a Chromebook (or, more realistically for that user profile, just their phone).

Power users? I have to assume my experience of often wanting or needing something outside official repos, or a newer version of something in official repos, is far from unusual. I'm not even that demanding a power user, and that's still a very common situation for me. What's worse is the more one chases system stability, the worse this problem becomes, since Linux distros mix the base system and user-facing applications all together (and the structure of x-window-system/wayland/drivers/GTK/QT makes it hard not to do this)