Are you on some sort of strong hallucinogent? The difference shown in pre and post skip battles is more one of scale than an actual exponential increase of power. Oro's fight against sandaime was one of the highest powered battles in the naruto verse; the anbu at the scene even commented on how the fight was on a completely different level and seeing how the world already knew a lot of insanely powerful guys up to that point, like all the resurrected kages, it's not like this was the first time ninja were exposed to high level battle.
Heck the previous great ninja war had raikage/bee and yondaime, amongst many, tearing up people.

The battles we are shown now is just a natural evolution of the show where everyone one that was weak as fuck got stronger.
Kakashi really hasn't gotten that much stronger and even so he's always been at kage level, same with gai and most of the other high level people.
Most of akatsuki was at that level as well, with the exception of pein and tobi, who are both special due to deus ex machina. Heck even Itachi who's fucking strong by himself, just happened to have 2 deus ex machina's in the form of that ultra sword and shield.

It's also been well established that it was sarutobi who was called the god amongst ninjas and the professor, not the 1st, 2nd, 4th or 5th.... you don't give titles like that out for no reason. Sandaime in his prime was evidently perhaps the strongest ninja the narutoverse has produced after the the sage of 6 paths. Also kabuto's edo tensei being more efficient doesn't mean oro's resurrected them weaker. Kabuto just has it applied on a massive scale and is able to improve the resurrection beyond what they were in their prime, effectively making them stronger than they ever were; oro's edo tensei didn't resurrect weaker versions.

Again, the strong ninja had a relatively minor power increase, while the weak punks got older and stronger. This effectively flipped the scale to all battles being high powered; this makes the oro/3rd battle seem less special.