Yeah, AUR isn't great because it's engineered as a second class citizen given the necessity of third-party tools like yaourt, and that the whole process of installation can't be done directly through the first-party tool (pacman), such that updating the main packages can trivially cause third-party packages to suddenly stop working. ArchLinux offers just one way - their way - when it comes to dealing with software versions and if the user happens to depend on some thing they want to keep around, tough luck, and hope that future upgrades don't force a breakage that requires a recompilation which may no longer work.

That runs completely opposite to Gentoo, where the first-party repositories are defined the exact same way as third-party repositories, and that updates to first-party libraries generally don't immediately break existing binaries because the distribution was built with recompilation requirements from upgrade breakages in mind. Since third-party packages are treated no differently (no second class citizen treatment), their first-party tool (emerge) can manage the complete lifecycle of "third-party" packages in the exact same manner (as opposed to needing any third party tools to manage the build). This alone reduces the mental bandwidth for the end-users that are managing their set of required packages for their systems. All this flexibility is ultimately part of the various reasons that got me to switch from Arch back to Gentoo.