They keeps saying it because they think it is the catch all defense. That it demises any and all complaints and criticisms any of us can lay out against what has happened to the Naruto franchise. It is like if you see a kitten kids show that is genuinely awful let say like teen titans go or powerpuff girls (let not get into a debate if they are good or not and just say they are bad for the sake of example) or a really awful kids movie. And when you point out how genuinely awful it is people just go "it for kids" which seem to mean "of course it's awful but we have such low expectations and respect for the intelligence of children we think they deserve to only get the absolute worst shlock we can think of."
Anyways who is Naruto target demographic? Shueisha is in the job of making money with their manga, so they will sell it to who every they think will give them the most profit. It has ran for over sixteen to seventeen years by this point the original target demographic of children are adults now even internationally. Also the kids now a days aren't gonna be as invested into the series as they would be for My hero academy or food wars both of which started in their life time so they can get invested in or one piece which is a huge cultural phenomena in Japan that everyone reads. Now looking at the last we can see that Shueisha clearly was targeting the international or more importantly Western or more accurately the US fanbase which was believe to be heavily supportive of nH. The problem is they weren't financially supportive of the series. So they instead shifted focus to the Japanese fan base (which they pissed of with the ending and ever after) by making Boruto the movie. The tihg is that the kids in Japan are once again they not interested in Bolt because it is currently running on nostalgia (which they do not have for the franchise) more then any interesting story, and the parent in japan who grew up reading Naruto are not gonna let their kids purchase Naruto volumes because they do not want their kids to be invested into something they cannot trust not to stab their kids in the back. Leaving the Naruto fanbase only with the Otaku the parasites and outcast of Japan.
Well funny thing is my niece tried to read one of the old vols that I still have and I told her it would be a wast of her time, I mean she got to the part which she saw Naruto and Sakura and what is sad is she was hoping that they hook up even asked me how close they get and she was 9 when she read the first vol.
It did make me sad knowing I had to tell her how bad it was that even she got upset and throwing the book away, I mean its what makes me mad that people like that think kids are all stupid.
