It has several commonly unphysical assumptions, including infinite conductance, "freezing" the magnetic field in a chosen frame, and assumptions about time and length scales.

"Effects which are essentially kinetic and not captured by fluid models include double layers, Landau damping, a wide range of instabilities, chemical separation in space plasmas and electron runaway."

That electrons are 1836 times less massive than the lightest positive charge carrier is neglected. Accelerated, they strike positive and neutral particles and knock loose more electrons.