In most incidences I've seen, "willpower and heart" for Naruto generally amount to some last-ditch combo that involves power/smarts... I mean, he only used a basic Rasengan to finish off God Realm, but he used quite a few setups to get there, and a lot of brute power just to pull it off (2 Rasenshuriken, hundreds of clones, bracing against Shinrai Tensei, and then a Rasengan to finish it...).
Willpower and heart just keep him fighting, i.e using his power/smarts, against all odds... in no way are they at odds with each other.
1 he doesnt deserve it
2 the only reason he has any power is because of the 9 tail fox
3 hes the only character whos maturation doesnt make any sense everyone else has to train months and months and months to perfect one technique but he can do it in days by the "cheap clone learn anything i want in a day method"
all the other characters have plausible cause for them to be as powerful as they are
in actual fact naruto is starting 2 use his brains more in the shippuuden episodes. We have noticed that he has FINALLY figured out that he can use his shadow clones 2 gather intel on the enermy that he is fighting. For example against kazuku when he changed to long ranged mode and was up against naruto. If he continues to think before rushing in he will be a danger to anyone that will fight him. Especially in sage mode.
naruto may be dumb but hes beaten plently of geniuss eg garra neji pain and meny more not bad for some one who people who call him stupid pluss i think the 9 tailed fox will be verry wise so no naruto is not stupid in fighting wise but in test wise yes
Coughs and sneezes spread mystery diseases just ask itachi and kimomaru to name a few
well for me naruto is smart at all, he may act stupid sometimes, but in his battles he is really doing his best.