Why, you ask? It is because Kishi has been constantly knocking and beating on Naruto for the whole of Gaiden (and perhaps even "The Last")!
Think about it:
Ever since chapter 699, Sasuke has:
1. kept his rinnegan w/ 6 tomoes (not to say that I wanted him to lose it)
2. gained dimensional shifting abilities with it
3. Learned shadow clone jutsu, as shown by the trailer (It is not like this is a hard jutsu to learn, but still this is another massive upgrade for Sasuke since Sasuke can now emulate Madara and make a susanoo army)
6. Got whatever that black lightning or other substance was on his sword in the trailer.
7. Even when he did seemingly get defeated, it was only because he was protecting his daughter.
Now how has Naruto been treated since 699:
1. He did show some new jutsus such as the golden punch, rocket rasengan and better chakara control to the point where he can casually make and throw rasenshuriken with one hand. This was all shown in "The Last" Some time after The Last he also became hokage. It has been all down hill from there though.
2. As shown during both "The Last" and Gaiden (and based on the trailer seemingly the Boruto movie), Kishi seemingly has eternally restricted him from using the powers of the other bijuus as well as the truth seeking balls and the version of RSM that he used against Kaguya. Restricting Naruto from using this takes away multiple things from Naruto:
Multiple elements such as magnet (which could be useful as a sealing jutsu), lava, ink (which can also seal), soap bubble, acid, coral, steam (which can be used for speed boosts and tremendous physical strength, probably even an attack itself), potentially sand, bug powder (or whatever Chomei uses), etc...
Truth Seeking Balls
The cloak which ties for the most epic in the series (along with Madara's).
3. Not only does Naruto get nerfed, he also becomes rusty and gets stabbed by a sword. He then has gotten no redemption in Gaiden thus far! Sasuke's slip up was redeemed by Sasuke being able to take everyone to the other dimension and then owning Shin with susanoo. Naruto hasn't done anything impressive in Gaiden!
4. Heck, Naruto has even been restricted from using jutsus he already had before RSM. He hasn't even used one rasengan in Gaiden! Not one! He hasn't used bijuudama either even though he's taken out Kurama's head in Gaiden! It has just been chakara arm central with a side of shadow clones.
I just want to see Naruto be epic again like he was in the fight with Kaguya
Ever since 699 and the Last... just why Kishi? Why?