He wasn't being sexist at all. Yeah, he wrote them terribly, but to accuse him of sexism is frankly absurd for you to jump to that conclusion because the character is a way so you think you can label it with a buzzword such as sexism.
Accusing something of sexism is such a subjective viewpoint because 9 times out of 10, they weren't trying to be sexist at all and now you have just falsely labeled them as a sexist which sadly hold very large negative connotations in today's world. Yeah, just because a female character is shown in a worse light than a male character in a SHOUNEN manga doesn't mean it's sexist or the author is sexist.
I have a rather high standard before accusing someone of an "ism", if you will, and even then there are nuances. Like I said, I don't think Kishimoto was being INTENTIONALLY sexist. I just think he did what he thought people wanted to see as opposed to what he SHOULD have done. And when ALL the female characters are hyped up only to become useless to the main plot and housewives to characters they barely knew (except maybe Temari)...it comes off that way.
Yeah, there are plenty of shonen and other japanese mediums that maybe could have done a better job with their female characters. The difference between them and Naruto is that the others don't specifically hype their female characters up inconsistently, and even when they do a bad job, it's not noticeable as a consistent pattern. At worst those others come off as disappointing, but it may have been for the best; they knew they couldn't do a female character very well, so they just focused on the others.
Ah, and I must admit, I'm curious about Kishimoto's sci-fi manga. Not because I'm hyped, but because he announced it as soon as Naruto was finished. And we haven't SEEN jack squat. Hiro MIshama took a break, and you know what happened? Not only did he start his new manga, but he's also supervising SEVERAL Fairy Tail spin-offs. That can't possibly be easy for him when just ONE manga is practically slave labor. But whatever you think of his works, I must commend him for working so hard.
I remember listening to the Mavcast, where the two speakers were NaruSaku fans (I believe they used to be members here) and they speculated over what happened. They mentioned Kishimoto put fourth several one-shots, and none of them were picked up.
Going by what he admitted, with most of Naruto's story being up to his editors, it feels like many others are nervous to work with him. While editors in the manga industry can be very controlling, I think MOST want to work with a mangaka who has a good idea of where to take the story as opposed to a yes-man.