You would probably also need to replace the modules as mentioned in Overriding package versions used by services - #2 by Mic92. Or you could try to pick just a subset of packages as described in Gnome 3.38 on latest release - #5 by jtojnar.
But either way, it will be too a lot of work catching all the incompatibilities. You would be better off just switching to unstable or trying it in a VM using nixos-rebuild build-vm -I nixos-config=path/to/your/configuration.nix -I nixpkgs=channel:nixos-unstable, if you cannot wait for NixOS 22.05 release.