I wasn't able to reply earlier but here is another angle on the question that goes along with what Kalosyni wrote:
As I see it, the core of Epicurean philosophy that gives life to all the rest of it is the "worldview" of how the world operates without supernatural forces, how there is no life after death, and so on. Those are things that don't change no matter what circumstances you may be in.
The ethics, while it is what we use to make day to day decisions, is much more -- totally in fact -- contextual, and how to apply it is based on the circumstances you are in.
What I think waterholic is correctly noting is that social relationships have changed dramatically in 2000 years. The people we live right next door, even in the same building, are often not our closest friends or even known to us in many cases.
So when we talk about "the importance of friendship" it is natural that how we interact with the people who we consider to be our closest friends is going to be a lot different than the way people related in the past. The benefits we get from friendship may be the same, but the way we interact has changed dramatically.
My point in this short post is that this should not be seen as a limitation of Epicurean philosophy as it is part of its flexibility -- the goal is PLEASURE - of which tranquility is hopefully a large part, but which we may have to dispense with for long periods if our circumstances require change.
So to echo Waterholic, how I choose and interact with my friends may be entirely different than the way it was done 20 years or 200 years or 2000 years ago. But the insight is Epicurus is that the goal is pleasure in a life that is all too short, and in which there are no divine gods or fate or ideal absolute virtues. If we start with that - which is the heart - then we can adapt Epicurus' suggestions as to how to live prudently to fit our own circumstances.