Russia is about to win this war of attrition. They are focused on destroying what little is left of the Ukrainian army. They are not focused on territorial gains.
Fastest way of destroying armies, is to surround and destroy them, ie blitzkrieg, not engage in WW1 style trench warfare.
What little is left? Ukraine has 900,000 soldiers with 1,200,000 soldiers in reserve.
Russia Ukraine
Estimated available manpower 69,002,197 18,187,531
Active soldiers 1,320,000 900,000
Reserve forces 2,000,000 1,200,000
Paramilitary units 250,000 100,000
https://www.statista.com/statistics/1296573/russia-ukraine-military-comparison/