Huh? Kaido was in his thirties... Even if this Kaido was weaker, the difference between "young" Kaido and the current one isn't significant.
Tbf current shutenmaru told kinemon the scabbards who didn't time travel are now 20 years stronger than kinemon's group.
And if we go by current shutenmaru's feat compared to kinemon's, the gap os pretty significant between them.
Now we know kaido is a nature freak,so it is only normal his growth rate during these 20 years is alot higher than that of shutenmaru making him most likely on a different level than what he was back then.