Thank you. You kind of just made my point. It's hard to explain what I mean and explain it properly. But yes characters in the manga said that the fight was one of the highest powered battles in the Naruto verse. But that was a character in the show at that time. From all the fights we have saw up until that point it was basically the most extreme. However even the common fights since then have been about as highend if not more so. Sakura and the older woman sorry I forget names... VS sasori was in my opinion a higher end battle. Garra VS deidara was fairly close... Both of those were only at the start of the manga after the timeskip. So as time went on the manga had to keep being interesting and before to much longer you can look back at how oro and the old 3rd fought and say you know what... I have seen chunins perform almost as good in combat. Many fights were like 2-5 times as epic and powered. The 1st and 2nd hokages were derp... they basically did nothing. A couple jutsu each with decent ti-jutsu combat.
Sure there are many characters who got a huge explained power boost during the timegap, those who got a less of a boost as well so for the most part it is understandable. But one thing to notice is that things like timegaps and so forth are used as a ploy to explain strength increases. Characters who are already in there 25+ years of age or even a lot older 2-3 years time should do almost nothing. However we see even oro do some insane things since then. Kakashi seemed to really buckle down and train during that time gap because while he was decent before the gap after he was simply amazing. Now he could fight Zabuza and Haku himself so easily. And most of theses increases are understandable but an other huge example and something EVERYONE needs to pay attention too if your reading this that really shows how fights come down to the fact that this is a manga that has to be read by viewers or a story in general is that many of the revived ninja in the recent war ark that is happening right now. 90% of the time if the revived person had an exclusive ark or extended combat moments back before they were killed the first time there fights now are quick and seem a lot less extreme. Like even though they should be as dangerous they are not. Or in the very least it is shown offscreen. But most of theses fights are still shown almost totally.
What am I getting to? Well take deidara for example... He got a huge fight more then one fight and lost so sasuke. But he got very little screen time and it was not the same since he was revived. And this is even a bad example because he actually got more then others did. A great majority of the people dropped like flys. Sure Itachi,Pain and some others who are still considered important to the plot had or will have more higher end battles. But since many of the revived ninja who were already featured before are kind of pointless there fights are not shown or more then likely they go out very quickly. Often losing there will to fight and turning to stone or fading away into dust Sasori is was of the best examples. And the reason is the writer is bored of them and it's already been shown and explained and there backstory and plot is done so it's just bothersome to the viewers and time consuming and boring for the writer to implement them as much. So the writer will find ways to write them off quicker perhaps even having some excuses but in reality they should have had more screen time and much more complicated battles. Sasori was a huge let down... But you know what! I was happy it was done the way it was done because I did not care. I want the manga to move forward more quickly. But a lot of things like timeskips, an the way jutsus work and other things while they might be cool and make sense a lot of any written material is done so on purpose to kind of move the story along and to prevent or cover up plot holes.
If the oro and old 3rd fight happened now for the first time it would be completely different. Because the understanding of what is an extremely high-end fight in naruto has changed over the years. A Manga takes years to write! The writer and viewers all go though a change and the story evolves. Pre-time gap kakashi probably could have beaten or done very well against the revived 1st and 2nd hokage judging from there performance during the oro/old 3rd fight.
Were the true strength of the 1st and or 2nd hokage even 1 on 1 could crush and murder the current post-time gap kakashi without to much trouble.