When the ground freezes, it allows offenses, but history has shown that Russia is better at it than Ukraine.
Seriously? The last nine months seem to disagree with you quite strongly.
I follow the war daily and what I've seen is Russia attacking, and Ukraine repelling the attacks. Not vice versa.
The notable exceptions are the Russian withdrawal from the north near the beginning of the war (while making advances elsewhere), Ukraine's counter-attack in Kharkiv oblast (which was before the mobilization and didn't get as far as it should have), and most recently Russians withdrawing from Kherson (which was kind of a special case, where Russia got itself stuck in an impossible to supply situation and was being bled to death).
Defending is easier than attacking. Especially if you've got time to prepare fortifications, which is what Russia's been doing for months; in Donbas, for years.