The Common Core does not neglect differentiation opportunity, and neither does it dictate or detail that children must be in one class over another; that is left up to each state. Under the Common Core as implemented in California, children may take Algebra with an Algebra teacher based on their individual ability. The entire Common Core specification for math can be read in one day.
The Common Core does dictate learning targets to be met for any particular official class, whether that is Algebra I/II or Geometry. The Common Core also emphasizes deep learning over rote memorization, but it critically does not require that all students must be at the same level. This is the central point of contention, and not whether the Common Core ought go even deeper.
As a detail, note that Californian classrooms may have around 40 children in a math class, and that penalties for classroom sizes end in middle school. These are the conditions under which math teachers must address individual variability.
Equitable Math would be a SOLID win for private schools and after-school math programs such as RSM.
That's not true; the proposed Framework model shifts from a focus on breadth differentiation to a focus on depth differentiation.
You could just as well argue that the existing approach tries to force all students to be “at the same level”, since it neglects the differentiation opportunity that the proposed framework focuses on. That would, also, be wrong, but no more wrong than your characterization.