Yeah....he doesn't have RSM anymore I'm convinced. He might have something in between BSM and RSM, but he'll never have a mode as impressive as the Madara/Kaguya/Sasuke fight again.
I think he still has the version of RSM that we saw in the war. It is just that I think Naruto caught it... the syndrome.
What syndrome you ask?
I call it... six paths nerfing syndrome. It happens to all those who awaken the six paths senjutsu or become the 10 tails jinchuuriki.
Why do you think 10 tails jinchuuriki Obito couldn't use Kamui, didn't use rinnegan, and spent most of the fight blocking, tanking and dodging stuff rather than attacking?
Why do you think Rikudou Madara got robbed of his truth seeking balls, lacked a rinnegan eye, and spent the entire fight with Guy tanking Guy's attacks without himself attacking at all when Madara could have just quickly ended things with stuff like limbo, bijuudama, genjutsu, having the shinju tree itself absorb Guy's chakara, storm element, etc...?
It is because of six paths syndrome! That is: Whenever Kishi gives a character RSM or juubi power, he must absolutely make sure to rob them of half of there arsenal, and make sure that the character suddenly forgets about the other half that they have remaining?
This syndrome had a delayed effect on Naruto because he is the protagonist and he needed his full power in order to fight Madara, Kaguya, and Sasuke. Now that the focus is a little less on Naruto and a little more on characters like Sarada and Boruto, the syndrome takes full effect! Notice that Gaiden Naruto has only used chakara arms (I do seriously mean
only chakara arms!)? That is the syndrome. Naruto hasn't even used rasengan in Gaiden! It is actually really sad.
Kishi, why did you do this? What happened to keeping Naruto and Sasuke equal? If Naruto has truly lost the RSM from the war, then it is sad to say, but:
Sasuke >>>>>>>>>>>>>>>>>> Naruto