Tbh, the installer was inevitable after systemd integrated a bootloader, crafted a paritioning scheme for autodiscovery, took over user and home directory management, and topped it off with an updater and "system extensions" layering system that some immutable distros are using.
I'm not saying any of this is particularly bad but it's been very clear fot a while that systemd just wants to be an OS. With immutable systems the "distribution" part of it is reduced to a build system, and everything else can be provided by systemd and flatpak.
The various Red Hat affiliated projects have so much more reason to call themselves the "OS" than GNU at this point. A Linux system with systemd for the init, systemd-networkd and NetworkManager for networking, GNOME for the desktop, systemd-boot for the bootloader, RPM/DNF as the package manager, etc. probably contains orders of magnitude more Red Hat code than GNU code even if the system uses glibc and GNU coreutils.
Partition autodiscovery is pretty neat. I did my archlinux install with it using this guide[0]. I have never touched /etc/fstab and I have had zero to worry about corrupting a boot with wrong fstab entries.
[0] https://walian.co.uk/arch-install-with-secure-boot-btrfs-tpm...