That's hard to recollect off hand. But one thing I find easier with Arch (and Gentoo, which is my daily distro) is to create complex partitioning schemes (e.g encrypted swap and btrfs subvolume mounts) and boot loader configurations.
Another example is a window manager with a somewhat complex display manager setup and a ton of supporting services.
PS: I don't consider Arch to be the silver bullet. For example, I always prefer Debian for servers.
The problem is that all of those interdependent parts and software that are dependent on it become entrenched. There is no freedom to replace individual parts with an alternative because something else will break. That's what I call 'Modular in theory, monolithic in practice'.