I don't like apt too as much. But, interface-wise, you can make it way better with Nala, which is a frontend for it.
NixOS is too complicated and demanding for most users, who aren't programmers or hobbyists, imo.
I prefer Fedora Atomic. It has the same pros (unbreakable, highly configurable with universal-blue.org, etc.) but feels way more user friendly.
I use it with Distrobox on top, so I can use my package manager/ distro of choice (turned out to be Arch btw) on a extremely reliable system.
For your case, you can replicate Mint by just installing the Cinnamon image from uBlue and applying some minimal tweaks.
Then you get the user friendliness from Mint with the flexibility and unbreakability from NixOS. Do you like the idea? Just in case you get annoyed by NixOS in the future 🙃