You said "Naruto can't learn s/t ninjutsu because he doesn't know the first thing about s/t ninjutsu. Yet in the manga, he has. The difficulty being irrelevant, as summoning jutsu is a s/t technique. End of story.
I would like for you tell my why Geniuses such as Kakashi & Minato couldn't add a nature to the Rasengan.
Naruto doesnt know the mechanics behind actual space time ninjutsu. Stop comparing a type of space time ninjutsu that anyone can learn, to an S rank space time ninjutsu that only 1 person after tobirama was able to learn. Why do you think it takes 3 jonin to do, why do you think in all the years tobirama was dead, there were no more ftg users. Naruto cant learn it, stop making excuses.
Minato died before he could do it, you know that. Why are you acting like naruto did rasenshuriken on his own. Kakashi spoon fed it to him. Kakashis ingenious idea to use shadow clones to speed up the learning process is why naruto learned how to do it. Kakashi could not do it because he has low stamina and cant use that same method. Naruto was blessed with the kyuubi from the day he was born, so he has the chakra for it. And even then, he only achieved it because yamato was there to suppress the nine tails so he doesnt go berserk during training. If kakashi had the stamina, he would have done it, as he is much smarter than naruto. And if minato lived a long life, he would have probably done it as well.
Naruto isnt a genius, he didnt figure out how to complete rasenshuriken on his own, kakashi laid out everything for him. Naruto didnt even know rasengan was an incomplete jutsu. He would have never added his nature to it if kakashi didnt tell him.