Exactly but still people call him weak on the base. Just wait! He will show OP Jutsus in the upcoming chapters!
It drives me nuts on how clueless and sometimes hypocritical people can be. They base Hiruzen, overall, on his performance against Orochimaru in pt.1 without keeping context.
1. Hiruzen was old, it was force fed to us multiple times by multiple characters including himself that he wasn't as powerful as he was in his prime. His chakra had diminished so he had to be careful, he was having a hard time lifting Enma, his performance was abysmal compared to his younger years, etc.
2. The powerscaling increased since pt.1, but then context is still supposed to be the same. Although the fight was underwhelming by pt.2's standards, it was stated in the manga to be a Kage-level battle.
3. Pt.2 Orochimaru, the one that toyed with Naruto and almost beat Sasuke while dying, was much weaker than the Orochimaru that Hiruzen fought. He was Minato's rival for the position of 4th Hokage, to which many people think he should had been Hokage instead of Minato, and has been deemed a threat to EMS Sasuke. Yet stated that if Hiruzen were 10 years younger that he would had beaten Orochimaru.
4. Even though he was older and weaker, he was still considered stronger than Ei, Onoki, Yagura, and Gaara Sr. And yes, Kishimoto intended on making the other Kages to be Kage-level.
5. Because Hiruzen was old and his chakra capacity diminished, he was forced to fight smarter and not harder, against three immortal opponents. He used Dragon Napalm to try to hit them all at the same time, used Mudslide Wall for defense, Enma for support, and a Shadow Clone+Reaper Death Seal combo for the win.
Kishimoto clearly hasn't forgotten about Hiruzen, all the hype he gave him has not been retconned out of existence. He even gave Hiruzen more hype in pt.2; having a young Hiruzen say to Tobirama's face that he's stronger, and the pseudo Rikudou Danzo said that he wasn't ever able to surpass Hiruzen. Even now he has been called "one of the strongest" in comparison to the likes of Hashirama, Tobirama, and Minato. Hiruzen will likely get the pt.2 powerscaling treatment and leave people wondering just how powerful he really was in his prime.
Then let's not forget about Enma. Apes are naturally stronger and more agile than humans, so a ninja ape is clearly going to be stronger and more agile than ninja humans. He may know other jutsus than just Adamantine Staff and Indestructible Prison Wall too.