Guys surely u would have noticed by now that the manga is very complex and kishi makes his characters have incorrect knowledge at times, even lie.
For example its was known by the 5th muizkage gaurds that sasuke killed zabura when he didnt.
Tobi told sasuke he did cause thr fox attack on konoha but we know he did.
Tobi said hes madara but hes not.
There many examples of this.
YOu have to consider the characters crebility to determine what is relaiable info. SOmething that kishi went into with how anbu handle their missions etc..
Its sounds ur selling kishi's work short to me.
Also if your gonna say the third hokage is the strongest hokage based from Izuka then why is kishi contricting himself with the entire part 2 of the series as Hasihrama is regarded as the greatest shinobi that everyone wants his powers.
Guys kishi makes his characters condirict themselves to set for an epic story telling experience. This creates plot twists etc.. So u shouldnt just take some random shinobi like Izuka to start undermining the hokages before the 3rd particluarly , hasihrama.
For example Tobi regarded hasihrama the strongest of his time. Thats signifact given tobi's powers and place in the story.
Jiraiya regarded Minato a genius only seen onece a decade. Again given Jiraiya place in the story u can say Jiraiya knew what hes talking about.
Itachi, Kisame,nagato, minato even Orocihmaru all acknoledged Jiraiya's proess as a shinobi.
Compare these statements to Izuka then u'll see what I;m talking about when it comes to a characters credibilty in the manga.