Imo this is a lame excuse. Some rolling release distros whose packages more or less equally up-to-date are far less brittle, namely NixOS and openSUSE Tumbleweed.
Arch's demanding nature with respect to being routinely updated follows directly from the fact that its package manager is stateful and unsophisticated (e.g., its dependency resolver is incomplete (will fail even when solutions are available, because dependency resolution is NP-complete and 'gotta go fast')).
It's totally fair to call this an Arch/pacman defect. Part of it is also lack of enduring hacks like Debian and derivatives use (long-lived transitional packages), which is a choice by Arch developers. A glance at the online Arch package listing and some example .PKGINFO files indicates that Pacman also doesn't support metadata like 'provides' and 'replaces' in DEB and RPM, which means the developers have fewer tools at their disposal for dealing with transitions like that, even when they want to.
Clearly many users don't mind all these tradeoffs, but others who shy away from Arch after experiences like that mentioned in the GP comment are totally right, as a matter of fact, to blame the design of the package manager for their woes.
We're not looking at the price of bleeding edge packages or a rolling release. We're looking at the price of 'keep[ing] it simple, stupid'.
Edited to add: the existence of the DUR shows that Debian probably doesn't fall on the right side of the complexity tradeoff for the purpose of maximizing user contributions. The same users who contribute to it could also create their own Debian packages, but they don't, presumably in part because it seems harder to get into. (It's not that bad if you use debhelper, but it is also clearly a crufty system that has evolved this way and that over time.)
So Arch's philosophy also clearly has other strengths. But imo we shouldn't give it a pass on the kind of fragility outlined in the GP.