When you are not constrained by the laws of physics, metallurgy, thermodynamics, Newton and a gazillion other things, you can make up fun, pretend “designs” that look really cool.
Explain why that is a “shitty” thing to say. It’s simply a fact.
Because you are dismissing the process that he has to go through to create this. It’s a freakin’ game. Your comment made his efforts seem less real than if he were working for NASA.
Maybe you did mean to sound like a sour old engineer, and if I misread that, accept my apologies. But in reality, you wrote that like an old guy suggesting “that’s just a picture.”