What to do when friendship has run its course? Nothing, really, just don’t pretend

Is this familiar? You have known someone for many years, and in those early days you both regarded each other as friends. But latterly, in the past few years, you feel you no longer like that person very much. It isn’t that you actively dislike them, it is just that you no longer find them interesting or good company — they are very much like those people to whom you are indifferent.
I can honestly say I don’t dislike many people at all. But I can also tell you that I am indifferent to quite a few people. I get on with them, because I tend to get on with most people. But that doesn’t necessarily mean I like them.
What I have outlined above has happened to me twice. It is rather disconcerting when it happens, but on the other hand I get rather jacked off having more or less to play act. The first friend — or perhaps I should call him a former friend — was someone I knew at university. On the face of it we were like chalk and cheese: I was the fresh-faced public school lad who didn’t know shit from sausages, he was the student radical/revolutionary who made much of his ‘working class roots’. Oddly enough, as I moved around the country, this chap would find himself nearby. I knew his first wife and was something along the lines of best man when he married his second wife. Yet over the years we were more or less officially friends, but I can’t say I particularly enjoyed his company. For one thing, I was one of his few friends who knew him in his student revolutionary days and I think this embarrassed him as he dropped the working class London accent and his speech became more markedly refined and middle-class. I remember one afternoon in particular: I had been invited to Sunday lunch (his second wife, who was an alcoholic and is now dead after falling down the stairs one night while, I suspect, very drunk, and I got on well and I more or less had a standing invitation) and after lunch we settled down to watch some tribute charity concert on TV which featured all the bands from — then — 25 years earlier. Well, I wasn’t very interested. I have never been one for nostalgia and all these bands, once long-haired and young, were now balding and middle-aged and had most certainly not taken to heart The Who’s sage advice to die while they were still young. We were drinking wine, and this chap got rather annoyed with me for not joining in the spirit of nostalgia. And I got rather annoyed for being expected to.
That was several years before we finally went our separate ways, but I remember driving home that night thinking that that was a friendship which had run its course.