Well, Russia definitely has a lot of resources, especially manpower, or in Russia's case cannon fodder. And in that lies the whole mystery. Times have changed and the situation is not the same as it was in the USSR, and mass mobilization is not an option anymore because it would signify a war, not a special operation, and mass mobilization without a direct threat is hard to push on the people without retaliation (and we know what happened to Russia when people were unsatisfied with their governments waging a war). So using the biggest asset the Russians always had was the manpower, not the technology or the sheer firepower, and when that main resource gets taken away...well, we get this.