You guys really think an MC will join the bad guys? Don’t be stupid.
You guys are too old for the target audience.
I can see why you would think that due to his personality not being that of someone who would defect.. but your argument is weak, if you can even call it one. Was Sasuke not a main character that defected for 3 years? And also lets say your opinion is based off of who we think he is in this current part of the story (both manga and anime).. Obito was the same way and look at what happened to him. Again another weak argument if one were to try to use that as a reason as to why he can't/won't defect.
We have a kid that has resentment towards his father because he disagrees with how he does things and just doesn't understand why Naruto is the way he is. The same kid also has two mysterious powers that probably make him feel like a freak. Once they start to become active again, it has potential to disrupt him and have him looking for answers/ways to control the seal and Jougan. This either means he leaves the village to travel with Sasuke, as he's currently the only one that knows enough about Otsutsuki to be of help.. or he's going to seek Kara/they will seek him. Now there's two ways he could do this. 1) is to defect from the village seeing it as something useless to him or 2) end up just going along with Kara as a double agent for the village just so he can learn more about his rare/mostly unknown abilities. Just think back to the intro to the Boruto manga that kishi wrote, or Boruto The Movie... or even some parts of the manga and anime later down the line. Boruto makes it clear he will walk his own path, a totally different one than Naruto. One similar to Sasuke. This is foreshadowing that he will share similarities to Sasuke. We already have some. Living in the shadow of someone (Itachi/Naruto), Having an unwanted/uncontrollable power (Cursed Seal/Seal/Jougan), Loss of nearly everything (Clan/ Foreshadowed destruction of the village)... The next thing that will happen is the lure of control/power/answers which in turn will have him leave, right?
Also, I have no idea what you mean by target audience...I didn't know there was a set target audience they were catering to. Kinda thought it was a mix as it's going to take a dark turn later on. Ya know, heavy themes of death etc?
Theres my actual argument(s) as to why it can happen and also why the age thing is objective and stupid to bring up.