I suppose then AAA magician Asha counts as a guy for you? And Airi who singlehandedly saved half of Atera by going one-on-one with a Rakshasa is immature too? Not to mention Jibril Ajes, Brilith's mother, who saved all of Atera during the Cataclysm? All immature, irresponsible and foolish girls, right? Then we have Primeval Goddess Brahma, who is so 'immature' that she keeps her cool despite all foolish wars and nonsensical bloodshed, and is actually the only Primeval God or Goddess still alive in the Kubera universe (= she is more powerful and mature than anyone of the other protagonists) Are we reading the same webtoon ?
Sorry for the late reply.
Yes, all of those are either immature or not known enough to be called mature. They are awesome, sure, but nothing in what Asha or Airi does seem mature as much as "i am badass and i have goals". In fact, in some ways, i would tend to say Leez is more mature than Asha.
I can't speak for Brilith's mom, but nothing we know of her shows maturity- and as for Brahma, everythign we know of her seems to indicate a lack of maturity (though we really don't know enough).