Let me preface my comment with the fact that I really enjoyed Man of Steel; but I can see that your criticisms do have some merit.
I feel like this is pretty nitpicky. Krypton is a completely different environment with what I'm assuming is a comprised of completely different cellular makeup. Further, it seems that a lot of their technology is intimately connected to life. For example, keelix was able to follow Jor-El's commands without any words being spoken. Also, the presence of advanced technology and the use of animals for transportation are not mutually exclusive, especially when the functionality of using animals surpasses that which is available at the moment.
I think this idea is more related to Clark when he's an adult, because Superman was not his identity at that point in the movie. In that scene he's supposed to be an adolescent, so around 16 years old. He's never really used his powers before and does not know what he's actually capable of or how invulnerable he is. If you have seen the animated movie, "Flashpoint Paradox," then you'd see what would happen if Clark is revealed at a young age. Pa Kent knew that if Clark were to reveal what he was at that age, people like Lex Luthor would exploit him and use him. The world is not a nice place to those who are different, and Clark had already experienced his fair share of torment. Further, I cannot state this enough, Clark was not an adult, he was a kid in that scene.
I actually love that they changed his attitude somewhat. They gave him an actual believable psyche. It's believable that someone given these powers, raised in a xenophobic and polarizing society would experience depression, anxiety, and become reflective about who and what he is, as well as, what his place in this world is.