Some here are mixing bootloader unlocking with rooting. They're not the same thing.
Asus broke bootloader unlocking, so you can only use the original ROM in the original state. You can't install a custom ROM or flash something like Magisk to root your device.
You can unlock without rooting or without installing a custom ROM. You can install a custom ROM without rooting. You can use stock and root. And you can use a custom ROM and root. But all this is only possible if you can unlock the device's bootloader.
Also, something I don't see people discuss enough: for security, you also need to be able to re-lock the bootloader after installing a custom ROM. Otherwise anyone can inject code into the system partition if they have physical access to your device, which would also compromise your encrypted storage. So if there's no way to reverse the bootloader unlocking, that's also bad.