Naruto is using Kuramas near infinite chakra reserves, Gai doesnt use jutsu so they are excused.
Kakashi on th eotherhand should be dead. In the Pain arc, just using a lightning clone and a raikiri used half of his chakra. Now he's got clones double raikiris, kamuis, going around. maybe Sakura healed him before he left
but what can you expect. Kishi now wants all fights to be on a HUGE scale. Kakashis small chakra reserves made his character and fighting style based onn observation and strategy, now that Kishi wants all fights to be huge godlike explosive dbzish crap, he has to ignore Kakashis small reserves if he wants him to tag along in this fight