Nothing is new under the sun. Reminds me of the good ol' CoreOS (the original, not the fedora-flavored, although it also applies), Container-Optimized OS from GCP and the likes of the new wave with Talos and Bottlerocket.

My only wish is that immutable filesystem, read-only rootfs and most of the system with just a FEW exceptions, atomic upgrades/rollbacks would be more and more widely encouraged, discussed and adopted.

Just eliminating the worry of root partition running out of space is a life changer. From the ground up any "traditional" linux distro will force you sit and design how to partition the disk sooner or later. The guys above address this issue (and a huge bunch of others) for you.