You need a lot of manpower to take control of a large city. You not only have to clear buildings, but you have to leave someone behind to keep the enemy from re-occupying the space you just cleared. At the same time you need to completely cut off the city from re-supply and re-enforcement. And then you need to find some way to get the population to submit, so that you can move on to other objectives. The tools to carry out such a mission haven’t changed that much in the last 100 years. You need men and small arms. What has changed in the last 100 years is that armies have gotten smaller, cities have gotten larger and citizens have access to the same lethal weapons as their occupiers. Even if the Russians had competent leaders and motivated troops, I don’t think they could do it. And they have neither .