It seems like he said that if Big Mom is truly done then she is overrated, I don't know if he meant as in character or as in power level or maybe both.
If
@RogersBase is coming off this in terms of her power level, I obviously disagree because I still think Oda at the very least did try his best to portray Big Mom as a very powerful character
However I don't blame him for being disappointed in her character after seeing how Oda has treated her.