You really don't know what your talking about.
First Naruto hasn't mastered his powers fully yet and won't until he gets more fighting experience with them, but as usual is learning very quickly and will probably master them before this fight is over.
Second you don't know how powerful the Eighth gate is let alone what a master of the Gates and Taijutsu could do with it.
Thirdly the Obito fight is a specific tactical weakness fight not a fight of pure power, so even if Naruto was stronger than Guy's Eighth Gate it doesn't matter if he doesn't have Kakashi's Kamui or a technique that is faster than Obito's mental reaction time, which Naruto does in his tailed form but he can't use it without breaking his own bones.
Finally the Gates are an enhanced form of Taijutsu to the highest imaginable level and is so taxing it takes the users life. Naruto has one technique on the same level as the Eighth gate and that's full power Bijuu Dama and that takes so much of his chakra he can't use it more than once without waiting an extended period of time and while Bijuu Dama is a single use attack, the gates can be used for an extended period of time without any draw back and a master of the gates like Lee or Guy can use the gates almost as long as they want before feeling the side effects while attaining the highest level of physical strength, speed, endurance, reflexes and taijutsu techniques some only useable through the eighth gate.
So remind me in what way Naruto BM stronger than Guy Eight Gate in what way when Guy's been holding his own so far without using the gates at all against Obito and the previous jinchuuriki.
The Gates are incredibly difficult to even learn and take years, Lee only learned them because he was extremely dedicated to learning and trained round the clock to perfect his skills and was a prodigy when it came to the gates, Kakashi can only get up to 4 and Guy can use all 8, and the reason they destroy a persons body and weaken it is because it stretches a human beings limit of raw power to the absolute maximum, by definition of what the gates do no human can be stronger than a human using the eight gates unless they have more potential than the person using them and they also use them with equal skill in controlling the power of the gates. The only whole in the Gates' power is it is possible someone using an extremely devastating and powerful ninjutsu like an extremely powerful Bijuu Dama explosion (Like the one Naruto used earlier in this fight) can be more powerful than the gates in head to head force and once the explosion went off if the gate user tried to push back the force of the explosion they would definitely die, I don't think anything is as devastating in power as a suped up Bijuu Dama, but Bijuu Dama has costs, but that still doesn't mean the gate user can't dodge the attack with their incredible speed and take the Bijuu Dama user out or take the Bijuu Dama user out before the chakra forms together or redirect a fired Bijuu Dama with sheer force back at the opponent before the ball explodes like how Madara did.
