First of all, parents are the main labor force of social production. At the same time, the geographical layout of the labor market has caused many parents to commute for more than an hour every day. It is difficult for them to participate in the whole process of children's education, and they must need the help of the elderly.
Secondly, it is unfriendly to support parents to raise children, whether in enterprises or in society. The time for children to go to school and leave school is similar to that for parents to go to work and leave work. However, there are very few standardized late-night care classes in society.
So to sum up, it is objective and inevitable for grandparents to participate in parenting.
As for the disadvantages of many so-called intergenerational education, I think even modern parents are possible. Because this question does not belong to ancestors, but whether education is scientific.
Therefore, as long as grandparents can learn scientific parenting knowledge, they will become the mainstay of family education.