>>512852246 (OP)
They've always been bad at it but more recently it's due to a series of political purges disguised as "reforms" of the army that have left it progressively less capable. Before Ukraine, being an officer in the Russian army was like working at Starbucks, a low-cost, low-skill job for young men to spend a little time in before moving on to better things. The high ranks are filled entirely with armchair generals and career politicians with personal loyalty to Putin and everything else is a revolving door.
Russian equipment is outdated, but then so is most of Ukraine's. They've been hamstrung through this war by low standards and poor leadership down to the structural level, which has invariably also impacted their modern doctrine and theory.
After the defeats of 2022 they basically threw out their entire modern combat manual and regressed to WW2 Soviet doctrine, which has proven far less successful against Ukraine than it did against the Nazi's.