There is no indication Kaido grew any stronger
- Kaido, and Big Mom(with young Whitebeard) were only mentioned to have grown stronger since their days of the Rocks, but there were no indication of when they actually peaked
- We know though that Kaido was in the Rocks 38 years ago, formed his crew 33 years ago, and fought Oden 20years ago. That means he had 18years to grow stronger before facing Oden+experience of fighting in the world strongest crew of the past
- In this batch of spoilers, it mentions that 25years ago, Kaido was trying to avoid being
military overwhelmed by Wano forces(mainly Oden+Hyogoro forces), which implies it was the main difference in the 5 timegap instead of individual strength, and military force plays a huge role in the quest to become a yonko, and thus may have more being a reason in Kaido's time to rise to yonko than his individual strength
- Big Mom(who was mentioned to have a cat and mouse relationship with Kaido) was mentioned to have been an unchallenged yonko for decades(so at least 20years) with herself only last meeting Kaido in decades(so 20years at least)
So sure, maybe current Kaido is stronger than 20years ago Kaido, but so far there is no indication of that