You can run a debootstrap and get a chroot environment from which you can customize Debian without the installer.
My point, which I now realize I thoroughly obfuscated, is that by only providing low-level tools and focusing on making them simple and transparent and well-documented, Arch makes its inner-working much more accessible to beginners, at the cost of maybe seeming impenetrable to the total noob.
You can also install a debootstrap binary for most other distros and bootstrap a Debian chroot system in less than 3min ; )
>I trust that all the smart people using debian are onto something.
The big contrast with Debian and Arch are their package maintenance policies and release cycles.
The Debian community strives for a system that works well together and is stable above all else. Software must conform to standards of quality and stability, might be modified by their maintainers to that end and will be staged through the whole experimental -> unstable -> testing lifecycle before being deemed stable. This is a big deal for systems that you rely on or that you'd like to set and forget. Having the guarantee that software Works and updates won't break the system are also important.
From my experience, Arch is much more liberal about their packaging and is closer to the Debian sid/unstable experience in that you have access to bleeding edge packages that work 95% of the time, but sometimes you need to get you hands dirty to get your system working.