Earlier quoted context omitted.
UNIX vendors didn't normally ship releases or updates that introduced dependency issues. Part of their job was doing testing and quality assurance, that's what you were paying good money for. Most such issues were introduced locally. A good sysadmin would know how to avoid dependency hell. For example this might include taking basic precautions such as testing changes in a chroot or development/testing environment, b…
The problem with dependency hell was more that RedHat back then didn't have such a thing as a "rolling release" or "testing" in Debian speak. So while "RedHat 6" worked fine, trying to upgrade (say) OpenOffice would require that you download the rpm from OO's website, which would require that you upgrade Gnome, which would require that you upgrade X, which would require that you upgrade glibc, and down the rathole. C…
There is no distro today that provides packages for all the software you will ever want, or the specific version that you need. At some point, you will resort to installing software from outside the officially-supported sources, whether from experimental or user-maintained package repositories, or from a third party in binary or source form.
Until recently, this was an operation that wasn't guaranteed to be easy or straightforward or risk-free. In the worst case, it could even screw up your system in ways that are time-consuming to diagnose and fix.
In the example you gave, I would conclude that OpenOffice didn't package their RPM well, because it ended up driving RH6 users down the rabbit hole. At the very least, they could have unpacked all the files under /opt and provided static binaries, or included all the libs in the archive. Many packages still do that today, such as Vagrant, which installs under /opt/vagrant and includes its own Ruby interpreter there.
Nowadays there are efforts underway to make installing custom software safe and easy, projects like: flatpak, OSTree, appimage, and snap. Hopefully we can reach a point where you can install whatever version of whatever software you want without breaking anything.