It's also constraining. Console makers dictated that RDNA must use a forward-compatible version of the GCN ISA. While AMD might have wanted to make some change

It's also constraining. Console makers dictated that RDNA must use a forward-compatible version of the GCN ISA. While AMD might have wanted to make some changes of some ideas that turned out to be less-than-optimal, they cannot because they are stopped by the console makers paying the bills.