Like Kakashi would even need the MS for that version of Naruto
He's vastly outclassed in actual speed and skill. Naruto had bigger chakra reserves and an insanely powerful jutsu above anything Minato ever had but spamming shadow clones isn't gonna solve anything without PIS with characters on that lvl. Minato goes without saying, Kakashi would undress Naruto....which makes Kakuzu's loss that much worse.
If Kishi was a better writer he would simply have emphasized the attack itself without fake hyping Naruto's overall fighting ability, but he dumbed down an S class opponent with 100 years of battle experience so Naruto can land the attack.