The effective use of tanks in combined arms warfare requires a good deal of training, planning, and skill in other areas, like achieving some degree of air superiority and a strong logistics effort. The Ukrainians stopped Russian tanks with cheap missiles, the Russians can do the same.
It's not as if the Leopard II is massively better than the T-82. It's better if used wisely. I won't be shocked if Ukraine digs a lot of these in as semi-mobile pill boxes, which would be defensive in nature. I can't quite see them mounting a real offensive like was seen in WW 2. I dunno.