Why is it said that disciple regulations are rubbish of traditional culture and Confucianism?

Confucius talked about filial piety and brotherhood, but the "Book of Filial Piety" does not have a high status in the Confucian classics.

It is not a question of whether "filial piety" is good or not. Confucianism is about the middle way, not just about loyalty and filial piety.

Is filial piety good?

good.

But nothing in heaven and earth can be excessive, as excess is never enough.

You cannot fulfill your filial piety to your parents by killing or sacrificing your children. All lives are equal.