You can't just send more and more soldiers into the meat grinder w/o caring about casualties and expect it to do you well long-term. One shitty, unexperienced soldier with no training requires as much logistical support as a well-trained one, is infinitely less effective in combat, and is way more likely to have crappy morale. Victory is basically off the table for Russia; the most they can reasonably hope for is stalemate in the country's far east.