Shinsusenju is big, but its power is too spread-out; individual Mokuton arms aren't very durable, hence Karin being able to demolish a smaller-scale version of the statue with only chakra chains.
So a basic punches from the kyuubi cloak clone is sufficient enough to destroy one arm.
Like I stated in the OP, do you think kcm naruto can produce 5k clones?
Well technically, he could, but they wouldn't be strong enough. 5k is a little much; he's obviously better off producing strong clones that can perform multiple techniques.
For instance, I think Naruto's KCM clones could probably beat Shinsusenju with a wall of Rasengans, similar to how he defeated Madara's Jukai Koutan.