Kaido, Shanks, and Mihawk and even Akainu are all equal or past the strength of prime Roger, prime Whitebeard, Xebec, prime Sengoku, etc etc. I'm genuinely not joking, I actually believe this. To many people overestimate the ever living crap out of the old gen and I'm here to stand on business and say that's all true.
Besides MIhawk and Akainu due to being pretty featless, we've seen enough proof Kaido and Shanks are capable of 1v1ing someone like Whitebeard or Roger in their prime and actually being able to beat them. Yeah Kaido lost to Luffy, but Luffy needed a whole team just to help him and had to gain an awakening just to win. Even while nearly healed due to awakened zoan perks of having fast healing, Kaido was still giving trouble to him even while heavily injured. And do I need to explain Shanks?