How is the world depicted in Ender's Game a dystopic society?

It is dystopic in some ways, talking about a future where an alien species attacked us and we have to throw everything into fighting back... kill or be killed. There are also limits on childbirth and children being trained as soldiers. Lots of things that seem just the same as they are now, but in other ways, it is almost a utopia though. No matter that Peter had to manipulate his way through... somehow, he got the whole world to unite under one leader. That isn't something that could even happen today, no matter what was facing us. Kids have a way to influence and change society, and for their thoughts and actions to be taken seriously. Those aren't things that can normally happen in our society either.