>Planet of advanced technology fully capable of star travel
>Don't, Just stay there and go extinct
Why are Kryptonians so dumb?
Kryptonian civilization had become arrogant, hidebound, and inward-looking, and had long-since abandoned its capability of interstellar flight. Their "perfect" genetically-engineered society was unable to deviate from its programming to save itself.
It doesn't make any sense. If you are capable of space travel on that level, the idea you could run out of resources is retarded, all resources are abundant. It's just a stupid doomsday cliche that you use up all your resources and destroy yourself.