The OG NMs arent on Krakoa though but in space, so its not like she couldnt have been utilized there. Kitty isnt allowed on Krakoa yet she had a role in a book. Besides Rictor's powers could be hazardous to Krakoa as well. Unless she's actively trying to harm it, I dont think Magma would be an issue to it. There are either plans for her in Wave 2 or no one wants to use her
I didnt get teenage vibes from them. They are in their early to mid 20s (except for Karma) and thats how they read