lol the womb thing was kinda joke. But actually I think there might be a scene in the manga that refers to reproduction being important but now I can't find it so I'm not sure.
Well even watching anime is a form of escapism really. The boys each only have 1 hobby in their lives and not much else (one plays trumpet, one likes computers and the other likes food). So they try out aliens as a bit of thrill to expand their hobbies. If they were science fiction fans I'm sure running around controlling an alien might sound like a bit of fun fantasy outside of their normal 'dull' lives. But the alien type that they are given is known to be addictive and so, at least for the boys, it becomes a bit like a drug addiction.
For Kumi and Kasumi, they have a few things that they're escaping. Kasumi generally is avoiding confronting the loss of her brother by putting everything of herself into continuing on with her award-winning activities. Kumi is avoiding responsibilities, others always depend and look to her, like being school president or looking after her mom. So for both of them Alien Fighting is a nice little time-consuming activity and something out of the norm to fill the lonely holes in their life. Hence why the Yellow Knife chooses loneliness.
I don't think Tomizawa had a particular message, he just wanted to portray realistic characters with real human flaws and realistic aliens. There is an interview at the end of Book 2 with him and he says a little about his reasonining for the story. He says to him the brutal/violent scenes in the book had nothing to do with anything like child abuse, childhood trauma etc. but that mainly he was trying to think of things from an alien's simple, animalistic and sometimes brutal perspective. And likewise for the characters, to look at it from a child's perspective.
But I think that everyone is allowed to take their own view on it. As some may identify with certain things and if it allows them to enjoy the story more by looking at it a different way then I think that is great. And it is fun to speculate and debate on what can be drawn from such stories.