Again, this is actually not completely the case. Take the polarizability -we do go beyond the Kohn-Sham independent particle polarizability, by adding Hartree (i.e., the bare Coulomb interaction in the integral kernel of the Dyson equation) effects in the RPA, and even exchange-correlation effects through the exchange-correlation kernel, which is also a density functional. Like Görling in contribution (2.3.2), you might object that this is TDDFT, but I would say it is linear response in the ground state, so we are talking about functionals of the ground-state density. Simply, we have derived this ground-state density functional using TDDFT, but who cares how we derived it once we have it? We could of course dream of finding simpler functionals for the polarizability, maybe even explicit functionals of the ground-state density, but since even the kinetic energy is so difficult, I wouldn't bet on this in the near future.