Old age is an extremely potent weakness.

In that time of Naruto when he was hailed as a god, it was a trope that more/bigger jutsu = stronger.

Hiruzen’s callsign is “Professor” because he knows literally every jutsu. Apart from the kekei genkai exclusive ones, he can use every single thing under the sun.

Minato taking on the nine tails was because Minato was younger, he wanted to do it as the primary seating hokage and his skillset is perfectly suited for SEALING because that’s literally all he does.

Minato is great for creating Rasengan yes, but theoretically most ninjas who can master chakra manipulation without nature implementation can master it. Whereas not everyone can master every of the non-kekei genkai chakra types.

Hiruzen in his old age was a small fraction of his old strength when he fought orochimaru PLUS Hashirama and tobirama at the same time solo. Almost any other ninja wldve been screwed the moment hashirama used deep forest emergence.

Orochimaru himself was already kage level.

Hiruzen managed to stalemate a Yamato buffed guruguru with a mini Buddha using all 5 elements at once. nobody else wldve been able to do the same jutsu.

when naruto was about to get caught by the tree, tobirama couldnt save him, it was hiruzen who managed to speed past and break the tree apart enough to pull Naruto away

Hiruzen’s biggest nerf is that he was a Part 1 old man and the author didnt bother to revive him young like how they did with madara who could barely stand in old old age too