It somewhat ruined it. And yes yes, I know some will say "Kaido got stronger in those 20 years"
And sure, I can agree to that, BUT to some extent.
Here is my issue, and why Kaido went down in ranks for me. Kaido had some mystery behind his "tough invincible skin" to the point most of us viewers when Luffy stated that "advanced armament haki which Rayleigh showed can affect Kaido if he learned it". Most of us thought that it's not going to work as easy as what Luffy suggested. Because we had the idea that " Kaido must have fought so many Top Tiers. But they couldn't do that to him.
We had the idea of:
1- Enma must be something special, a cursed sword, something about the sword so mysterious that it can penetrate any defense, including Kaido's skin.
2- Law's DF may play a role in Kaido getting wounded by other normal attacks, as immortality subject was brought into the table.
And we and we had this HUUUUGE expectation of how hard it is to wound Kaido, and it's not what Luffy's solution was.
But the reality after chapter 970, is that Luffy was actually on point. e was 100% right. And it is as simple as "learning advanced Armament Haki" will allow you to strike Kaido down.
with 970, Ame no Habakiri scarring Kaido, made Enma has no "Special mysterious powers" and it is as simple as Oden simply had strong advanced haki to cut Kaido with ANY good level sword.
Secondly, Kaido's immortality "was proven to be false" with him being wounded heavily and can be damaged.
Thirdly, I understand Kaido could have gotten stronger in those 20 years, BUT it's not the issue here. The issue is that Kaido is feared for his invincibility, something he had OVER 20 years ago. The legend of his invincibility did NOT come after this fight. It was BEFORE. So, even in our current time, if Oden landed the same strike, Kaido would be 100% wounded.
Which is why, in terms of expectations and ranking, he dropped for me. And it became MUCH MORE believable that many characters like the admirals and other Yonko to wound him EASILY. Because simply All admirals (at least the original trio, showed advanced armament haki).
So, what I'm saying is, what made Kaido (SPECIAL) in our eyes, was braught down in one chapter by Oda, because so many characters right now seem to have the means and ability to injure Kaido.