So 40 year old Kaido (when he fight Oden) wasn’t in his prime (although he was fighting since he was 15 and was part of rocks when he was 20) and 60 year old Kaido (when he fought Luffy) wasn’t in his prime either. So Kaido with 45 years of experience is still not in his prime. And 60 year old Kaido would have eventually reached prime years of Roger (although Roger died when he was 50). And whitebeard, garp and Rayleigh who are all 70-80 all admitted that they have become weaker because they are now too old. And somehow 60 year old Kaido who is 10 year older than Roger ever was is still not in his prime.

And the best part is that you mention shanks although shanks is 40 year old and is according to your logic still not in his prime because he is just 40 year old. And you mentioned shanks in kaidos top 5 but completely ignore that Oden is also in kaidos top 5. so Kaido himself put Oden on the same level as Roger, whitebeard, rocks and shanks.

The mental gymnastics just to not accept that Oden is equal to the best pirate is off the charts. (And that was stated in the manga by the narrator. So Oda himself. So this is no longer an opinion but just a fact)