I suppose it's alright to forgive the lack of development when it comes to Misato and Asuka (although I still dislike this as well), since the original has some carry over (although Asuka is like a completely new character in the rebuilds).
I think you might be assuming too much if you think that there's "carry over" from the originals. If an aspect of the characters from NGE does not appear in NTE, then that means that it is definitely not
a part of their characters in NTE. The fact that Asuka is a "completely different character" is merely evidence of the fact that NTE asks its audience to start from scratch when viewing these characters. The audience is not learning something new about NTE Misato by watching NGE Misato. The two characters are not the same, and therefore don't share the same exact details. What's left out of NTE is removed for the interest in building a new character, not for the sake of shortening the work.
Expecting NGE to carry over into NTE is like expecting Micheal Keaton's Batman to carry over to Christian Bale's Batman. Yes, they're both Batman. No, we're not supposed to assume that the Joker killed Batman's parents in Batman Begins
like he did in Batman
. They are essentially two completely different characters. What's lacking in one story compared to the other is lacking for a very important reason. What's lacking in Misato and Asuka's backstories are also lacking for a very important reason. There is no carry over.
Mari's character simply forces the NGE fan to come to terms with this fact in the most blunt ways possible. It allows those familiar with NGE to see a side character enter the series without any unfairly assumed carry over from the original story. This is probably why she is such a divisive character. When you see Mari and ask questions like "Where did this character come from?" you slowly start to realize that these are questions that you should also be asking for Misato, Asuka, Shinji, Gendo, and the rest of the recognizable cast, which threatens the nostalgic feelings we have towards NGE. This realization of unfamiliarity finally comes to fruition in Eva Q, where only a small handful of the characters are recurring from the original series, and an even smaller handful of those recurring characters look familiar to the NGE viewer. This is probably why Eva Q is just as divisive of a film as Mari is as divisive of a character in the fandom. Not only is Mari Makinami there with no recognizable traits from NGE, but the characters Sakura Suzuhara, Kōji Takao, Sumire Nagara, Hideki Tama, and Midori Kitakami are tossed in without any NGE recognizability whatsoever. These unfamiliar characters function in an equally unfamiliar organization called "Wille," who's mysterious origins cause many viewers to realize, even subconsciously, that the origins of Nerv or Seele are equally as mysterious in NTE.
Not only do we have unfamiliar characters operating in an unfamiliar organization, but they are also interacting with other organizations familiar from NGE that seem to have nearly unfamiliar goals and origins. (I can't remember a single character in NTE mentioning Gehirn as a predecessor to Nerv. This suggests a completely different Nerv all together.) Nerv looks desolate yet Gendo thinks things are still "going just as planned," Seele monoliths are dismounted yet everyone seems to be okay with this, and there's a key in a briefcase instead of an embryo in Gendo's hand that may or may not be used as the catalyst for Gendo's end-game scenario.
Both Mari and Eva Q are equally as unsettling for the NGE viewer because they reintroduce the sense of unfamiliarity that we had back when we watched NGE for the very first time. Mari and Eva Q are equally as frustrating for the NGE viewer because it took us over 10 years to familiarize and solve the mysteries of Eva, and these new installments in NTE threaten that sense of accomplishment by revealing a completely different set of unfamiliarity and mysteries in the Evangelion franchise that need solving.
And most the unsettling concept of all is that we might have to come to terms with the fact that, just like certain aspects of NGE, there might be things about NTE that we will never completely understand. All of these fears and anxieties are all summed up in the unfamiliar character of Mari Illustrious Makinami and the floodgates of cluelessness that she unleashed upon us by her very existence in the series.
We don't know shit about Evangelion all over again, and it's all Mari's fault.