  We evaluate the full opacity dependence of collective flow in high-energy
heavy-ion collisions within a microscopic kinetic description based on the
Boltzmann equation in the conformal relaxation time approximation. By comparing
kinetic theory calculations to hydrodynamic and hybrid simulations for an
average initial state, we point out shortcomings and inaccuracies of
hydrodynamic models and present modified simulation setups to improve them.
