You serious, Bogard? Just accept it that he can use it for a few seconds or sporadically and move on. He says he 'isn't good at Senjutsu', yet you claim he is the 'perfect sage' going against the manga facts - Perfect Sages are able to actually maintain their SMs longer. He says it takes too long to Knead that Chakra - meaning balancing Natural Energy and Chakra to Create Senjutsu Chakra - yet you claim he can enter instantly. You made up both of these things.
He is so bad at both of these aforementioned points that he never bothered using it against Obito and others, as 'it takes too long and he isn't good at it', which would explain why he didn't opt for it against opponents even on war-zone - he didn't have much time on his hands, not even when he left Naruto and then came back with Kushina as well. He had time - a lot of it - both times, yet, since it One takes too long, Two he is not good at it at all, three he cannot maintain it for more than a few seconds, he didn't opt for it.
This thread is far too ridiculous even for you. Guess what? Naruto was shown talking whilst gathering NE to make FRS for Madara, when he was pulled out, Kabuto was talking the whole time and was moving as well, even Hashirama was shown talking. Naruto even tried entering SM whilst running but he turned into a frog too soon. It's obvious that he might have accomplished it, if he was given more time as Pein attack happened not long after.
Just ... stop.