It's not as simple !
Luffy G4 was superior to Doflamingo and in this form he can manage a good fight against Kaido.
But the difference is that you can have any combat skill you want, against Kaido if you don't have mastery of advanced CoA or coated CoC... You will loose.
Devil fruit (Law, Kid) or really high power attack (Zoro) can help, but I don't think can be enough to fight in par.
It's only when Luffy could use them that he could fight equaly, he's already a combat genious, in pure skill he was already in par, he was just missing the good tool.
If Doflamingo had mastery of advanced CoA, or coated CoC (he got the potential to), the fight in dressarosa would have been a low dif for him.
Because with those tools he could hurt badly G4 Luffy, what he couldn't.
Law beside awakening "Kroom", didn't show better combat skill than Dressarosa, or more Haki mastery.
I'm not sure actual Law could still beat Doflamingo, it would be a more equal fight, but Kroom as perfect it is against slow opponent like Big Mom or Queen.
Against more versatile fighter like Doflamingo, Katakuri or Marco, I have big doubt... I don't put Dofly on the same tier as Marco and Kata, but more about the fighting style wich is similar, like quick polyvalent outboxer.
I still don't see him having the physical feat or combat skill to fight them on par in close combat... And if he miss his Kroom attack, it use so much stamina that he will be just fresh meat to them...
