I don't use them for most things I install but proprietary apps I want sandboxed or programs that have weird issues with dependencies I grab the flatpak.
For me on Arch, Flatpaks are kinda useless. I can maybe see the appeal for other distros but Arch already has up-to-date versions of everything and anything that's missing from the main repos is in the AUR.
I also don't like how it's a separate package manager, they take up more space, and to run things from the CLI it's flatpak run com.website.Something instead of just something. It's super cumbersome compared to using normal packages.
I also prefer to get my software from the distro's repos, but for software from third parties, flatpak adds a security layer, making it more secure when compared, for example, to aur.
I use Ansible all day. For work. Oh, god, is it sad compared to everything else in the space. RedHat had the choice between two in-house products and they chose poorly.
It can do lots of configuration and [set up] and install flatpaks.
We had that 20 years ago, just with a different product. The state of the art is now two generations newer.
Well I know Ansible and it works for my needs. I briefly used Nix and it was worse. Ansible is nice because you can just install ansible and then apply a playbook.