It might be still there as the successor of the USSR (whatever that means), but it does not hold the same amount of power to defend its interests. And it holds no control over the lost territories. Those territories no longer belong to Russia (the successor of the Soviet Union). If those lost territories want to join NATO, what can Russia do about it?
Let's say that you have a family and I sign a deal with you that I will not do business with your family without your permission as the head of the household. If somehow your wife ends up divorcing you, can you stop your wife or your children from doing business with me? Can you blame me if I do business with them? Same story.
That's what happens when you get zogged by letting an infiltrator like Yeltsin in under the cloak of MUH DEMOCRACY.