Put another way, I would think that individual engineers would be better off learning the underlying tech and the tools provided that go with them. I think it's very possible that Flox (or devenv or...) reaches EOL, or ceases to track nixpkgs appropriately, or any of the other ways that software rots. Where nix develop is going to last as long as Nix Flakes do, and there's incentive to provide a migration path to whatever's next.
Even more important: every abstraction is going to leak. Maybe the Flox CLI "looks" cleaner or whatever, but in the end you'll still need to learn Nix to use it effectively. Why learn twice as much stuff as you need?
I'm extremely amused that one of the trials here was "how do I measure 6 liters of water with a 12 liter jug and a 6 liter jug?" and the article completely glosses over the fact that the framework doesn't help GPT find the simple answer "fill the six liter jug"
"A few days ago, I came across this problem" - well, volume 4A of The Art of Computer Programming was published in 2011, which gives a pretty good treatment of the Langford Pairs. The author might've made their reference clear, and called out that the Python implementation was their own contribution
Even more important: every abstraction is going to leak. Maybe the Flox CLI "looks" cleaner or whatever, but in the end you'll still need to learn Nix to use it effectively. Why learn twice as much stuff as you need?