Yeah those were factors but age was his biggest problem as he stated. In fact Rasa the 4th Kazekage fought Orochimaru with his edo tensei and Rasa along with his bodyguards were killed without landing a single scratch on Orochimaru. So Hiruzen did a good job.
What part of him was reconned? And being the shinobi god or God of shinobis doesn't mean you're the strongest shinobi at all. It's just a titled for those who's will has been inherited by all the sinobi's across the world.
God of Shinobi at the time was clearly meant to claim Hiruzen as the most powerful ever(or at least one of), and that was backed up by Kabuto/Orochimaru's discussion after the fight about Hiruzen being the strongest of the 5 kage, even at his old age.
Being a kage-caliber ninja in part 1 actually meant something, too. Country-destroying powers weren't thrown around like they were in part 2. The only two people in part one that were put on Hiruzen's level were Minato and Itachi(slight arguments could be made for Jiraiya and Orochimaru, however Jiraiya and Orochimaru were both put on tiers below Itachi by other character statements, and Hiruzen's win vs Oro/Hashi/Tobirama combined puts him on a tier above, speaking solely in terms of part 1, not factoring in anything that happens in part 2, including Hasi/Tobi power ups).
If you go through and read part 1 again it's pretty cool how Kishi laid out the power scaling. The top being:
Hiruzen
Itachi
Minato ( Possible that Itachi and Minato were meant to be ranked even above Hiruzen, as the very first page of the
You must be registered for see links
, which would have included Hiruzen, and Itachi
You must be registered for see links
. However, worth noting that still would have been a retired and somewhat past his prime Hiruzen, so maybe Hiruzen in his prime could also match the feat? Who knows.
But yeah, Hiruzen was meant to be at the top of(or at the very least alongside Minato and Itachi) the food chain in part 1. That was retconned when everyone and their brother became as powerful as kage in part 2 and some wound up with mountain leveling techniques.