I don't think anyone's ever said Naruto was stupid, or even debated his intelligence...it's just that it's underplayed in the series. I mean lets look at it from a strategic point. Naruto Vs. Neji in the Chunin Exams using the hole from Shikamaru's battle with Temari to hide and Jawcrush Neji... When Naruto fought Kakuza we saw just how smart Naruto was tactically when he head-on attacked to gauge Kakuza's strength and see how many clones he would need for a successful distraction. Fast forward then to when he fights Pein and Naruto develops a near perfect chain of distractions and attacks in his final Rasen-Shuriken barrage that involved him transforming into a Rasen-Shuriken to take down the Preta Path...And lots not even get started on how he transformed into thousands of boulders to trick the Deva Path...so yes, Naruto is extremely smart, it's just underplayed.