Why has the Russian Air Force so far failed to achieve air superiority in the war in Ukraine? The Ukrainians have so far managed to shoot down 88 Russian planes and helicopters

One of the unexpected surprises in the war in Ukraine so far is the poor operational capability of the Russian Air Force, which is reflected in the fact that Russia has not achieved air superiority in the war arenas in Ukraine.
On the eve of the invasion, the Russians concentrated 300 fighter jets on the borders of Ukraine, However, these aircraft failed to achieve air superiority. The Ukrainians have so far managed to shoot down 88 Russian planes and helicopters.
Western aviation experts attribute the poor performance of the Russian Air Force to this That Russian pilots train only one hundred hours a year, only 50 percent of the training time of pilots in the Western Air Force.
Western experts also say, Because the Russian Air Force command lacks experience in planning and coordinating complicated operations of operating a large number of aircraft in real war conditions.