I guess recreating those cloud shaders would the hardest part. They look really god for running on a phone... The rest should mostly just be sculpting and modeling some fancy ground to walk on... And the amazing music obv... So maybe it's not tgatbeasy after all... Godot should make the cloud shaders easier, using their premade Voxel-volume renderer..
I'd say I'd love to get into Godot enough to try to make a Sky clone but knowing me I would be obsessed with it for a day and immediatly find a different obsession the next day >v<
I have once made some kind of grass shader using GPU instancing in Godot. Here is the vid. I feel that using and knowing Godot is a pretty useful tool to have if ya want to quickly whip up some UI design stuff and get a program out quickly and on many platforms at once. I've made some pretty bad game jams in the engine and it's really great.