The problem wasn´t Kid or Law, both performed pretty good.
The feats which both pull out been amazing, awakened and good skills.
Big Mom was the problem.
Yes her endurance was insane, but everything else was very disappointing.
She didn´t used adv CoC, she didn´t used awakening, she didn´t used any attack who was looking insane, Law awakened attack legit was looking far better then all attacks of Big Moms, nothing what she shown was Yonkou worth...
Kaido vs Luffy was great because Kaido had everything, great attacks, great moves, yonkou worth attacks, insane haki...
We didn´t see none of these with BM vs Kid and Law...