Flatpak is mainly for packaging desktop apps, whilst snap can update the entire distro (kernel, mesa, system apps, cli). Snap does things Fedora needs rpm-ostree for.
In my opinion docker isn’t as useful for cli tools. I need easy access to many little tools, and this results in me having one container with everything. But that doesn’t work well with network capture etc. In the end being able to install packages system wide quickly is really useful.