I’ve always heard the people parent the way they were parented. so people who have good grandparents have a leg up. 
Personally I believe that no matter how bad your parents are, each generation attempts to improve and most succeed. 

The thing is nobody starting off in the same place from the same standardized even starting point because it all depends on what your parents gave you.   

The other thought, there’s so many variables involved in parenting that even an individual parent isn’t starting from an even starting line.