Ahhh this is still one of my worries. But for every 5 times I reach out to an old friend to reconnect, I get an answer at least 3 times. Although we may no longer share the closeness we did before, I do value the time we had together as friends highly.
My biggest issue is being too nostalgic/sentimental. Friend breakups or drifting-aparts can hurt almost as much as romantic ones. And no one really talks about those lost relationships.
Thanks for bringing up an important frame of reference when it comes to friendship!