I have to disagree with your experience, it’s not been mine at all. My friends and I may have been more selfish when we were younger (we’re talking 10-15 years younger than the SATC characters) but we grew and matured together. Also, not everyone gets married/has kids, so do they just have to keep the tit friends?
I think the main reason us older millennials and young Gen X who were teens/early 20s when it came out didn’t pick up on the selfishness is that we were just a bit blindsided by how amazing their lives seemed! I know for me, watching SATC as it went out on C4, I just wanted to be as rich and glam and empowered as they seemed when I got to age 34. Every other 34-year old woman on TV at the time was a housewife or a frazzled mum. I overlooked a lot of their crap qualities because I found their lifestyles aspirational, and their attitude to sex and relationships was revolutionary at the time.
Women I’ve spoken to who were the same age/older than the characters say much the same thing: the show was so zeitgeisty and aspirational, plus such an original representation of women, that they didn’t really think too hard about what a witch Carrie could be.
Also, a practical thing but I think you notice more about characters when you binge watch a show. We were watching an episode a week back then! More time to forget stuff in between!
I actually don’t hate the fact that Carrie is often a bad friend; I do think most of us are bad friends at points in our life and it is somewhat realistic. I have more of an issue with Carrie’s shallowness, which went through the roof in the two movies. It felt as if the show was saying women can’t be interested in fashion and also have depth.