Why is separating class ind struct is bad?

[Suliman via Digitalmars-d]

Here on forum I have found very interesting mention from 
Alexandrescu that:
"Rust has two advantages I can think of: it doesn't have the 
struct/class split that D does". Could anybody explain why it's 
bad, and maybe till Volta in WIP it's not later to change it.

Could anybody explain what this mean and why this way is not 
modern?