Sorry for the harsh words but you don't have any idea what you are talking about.
Some examples: managing patches for applications is doable with NixOS. With overlays they survive updates and if they no longer apply, build fail before they can have production impact. Doing the same with docker is a nightmare and different for every dockerfile without a common interface around it.
Ansible takes the previous state of the system into account which is terrible if you want to manage it fully declarative. Worst case in NixOS you do a reboot and your config applies almost no matter the previous state.
And that you can leave something running without maintenance is naive and it will start to slowly rot.
Some examples: managing patches for applications is doable with NixOS. With overlays they survive updates and if they no longer apply, build fail before they can have production impact. Doing the same with docker is a nightmare and different for every dockerfile without a common interface around it. Ansible takes the previous state of the system into account which is terrible if you want to manage it fully declarative. Worst case in NixOS you do a reboot and your config applies almost no matter the previous state.
And that you can leave something running without maintenance is naive and it will start to slowly rot.