A big factor is Ukraine still had a number of Soviet made S-300s and older Buks. Those things are very effective and can shoot down even modern aircraft, includ

A big factor is Ukraine still had a number of Soviet made S-300s and older Buks. Those things are very effective and can shoot down even modern aircraft, including Russian ones. The Russian strategy has been to use standoff weapons (to great effect). Why risk your planes and pilots when ballistic missiles and kamikaze drones will get the job done? And remember, Ukraine is the largest country in Europe and the most armed and well trained. They are not Iraq or Vietnam.