I think your concern is legit, but you are also showing some misunderstanding about Naruto.
First, not everybody can use the power of the biju the way naruto is using - that is stay in human form to make a bijudama, or spam any amount of Kyuubi chakra while keeping your body the same. This is also Naruto's own power, meaning he has the body that is a perfect vessel for any type of chakra.
Second, Naruto is currently using his own power, and I will prove it in a very long thread with evidence from the manga. Going straight to the conclusion, my claim is that naruto had always had two source of Biju chakra: (1) from Kyuubi, and (2) from himself with the evidence being the six line on his face. For now, I cannot tell you if that chakra was from Kushina or Kyuubi, but fact is that naruto will have biju chakra even if he does not have a biju. Right now, the BSM eyes Naruto has is from his own biju chakra (2), and I will confirm this tomorrow if the current spoiler is true.
Next, only people who bet everything on KKG will actually not understand Naruto's power. Unlike those who are born with KKG that give automatic jutsus, others need to learn formula for their jutsus. All the student in the academy included Sasuke learnt their clan signature jutsus from their parents. Naruto who did not have any parent couldn't learn any of both his parent techniques. Thus, no matter how proficient he is, and no matter how much chakra he has, he will only use the little he was given or he stole - Kage bushin and Rasengan. These two jutsus are the certificate of Naruto's own power, and show that he can actually do any type of jutsu because they demonstrate massive chakra and ability to perform the most difficult shape manipulation. In case you have doubt, the lava FRS will demonstrate that Naruto can create any combination of chakra nature without difficulty. Some people are saying that it is because of Son Goku, but in the wrong way. Son Goku only gave naruto the formula to do the nature transformation that gives lava. However, Naruto is the one combining the different nature element to create the lava. In fact, I have predicted that Naruto will become Rikudo whether people like it or not, and this will start by mastering all the jutsus of each individual Biju.
Oh wait: In my opinion, mokuton is not a KKG, and Lava still is not a KKG because anyone with load of chakra and good control can make them. Just see Naruto do Mokuton if someone gives him the formula. For example, Bijudama is a mixture of 8:2 dark and bright chakra. Naruto created Bijudama by himself after Killer Bee gave him the ratio.