You're only considering the boot process. The initrd/initramfs serves to provide a minimal userspace required by more complex root storage arrangements before

You're only considering the boot process. The initrd/initramfs serves to provide a minimal userspace required by more complex root storage arrangements before we can pivot root. Sure I can reboot a system with hosed dynamic libraries into its initrd and use that userspace to try fix things. But I can also reboot onto any other rescue medium. The moment you've introduced a reboot into the recovery process there's myriad solutions, the introduction of the initrd didn't make a significant difference in this regard. The historically statically-linked /bin /sbin stuff (yes, once upon a time not everything was shoved under /usr like the post-systemd world) could be used to fix broken dynamic libs without even requiring a reboot.