I agree with the shift happening around the 1990s. I was born in the 70s and my childhood was definitely not child centred. I had my children between 2005 and 2014 and life is certainly more child centred now. I read something like this in one of Nigella Lawson's books - "when I was a child adults are in charge, now I'm an adult children are in charge so it's NEVER been my turn!". It's quite funny but has a ring of truth!
I certainly wasn't neglected as a child. Was well cared for, privately schooled etc. But the dad was the centre of the house and everything revolved around him. It was one of the reasons I didn't ever want to get married, lol. We were expected to do as we were told, not answer back, go to bed at 7pm so the adults could enjoy some peace etc. We fitted in with their lives and what they wanted to do. We did some activities but they were usually ones chosen/approved by parents (tennis/ piano/ guides). I wasn't bothered, I was quite lazy and a homebody, happiest at home with a book or tv (even that was strictly limited). We spent a lot of time not being entertained or actively engaged with by our parents. I don't think that was a bad thing to be honest. I'm very happy in my own company and rarely feel bored.
Not so good was a lack of emotional engagement. My sister and I both worried/got anxious a lot but the attitude was "pull yourself together and count your blessings". As a result I bottled things up and never confided in my parents. They didn't seem interested in what we were passionate about - all I can remember them being interested in was school work/academic results. I now think (since my own son was diagnosed) that I had/have ADD and feel quite aggrieved about all the times my parents berated me for being lazy/ daydreaming/hapless. To be fair people didn't really know about the range of neurodiversity in those days but I can't imagine not noticing that my child was actually "different" or struggling.
However, I think things have gone too far and I'm appalled by the number of children I see ruling the roost or not expected to be bored or hungry for even a few minutes. I try to strike a balance with mine. It's hard though and I certainly don't always get it right. I do insist on them entertaining themselves some of the time, but I also spend a lot more time engaged with them than my parents did with us and encourage them to tell me any worries or problems that they have. I invested a lot of time, willpower and money in unravelling my son's learning and social difficulties (HF ASD and ADHD). They aren't anything like as indulged as many children we know. We are quite well off but days out to stuff like theme parks or meals out are a treat rather than a typical weekend. I think if we did that all the time that stuff would never seem special. They also rarely get new toys or gadgets except for Christmas or birthdays. Some kids we know get bought stuff every weekend. Our kids do a couple of weekly activities each - chosen by them - except swimming lessons which were not negotiable. Some of their friends do a different activity every night of the week!
Why have things changed though? I think being taught in the 80s that women can "have it all" was a huge factor. Women who chose to give up a career for their children then felt they had to make a career out of motherhood in order to justify it. Career mums felt judged and lavished quality time and activities on their children too.
Also better contraception and it being more socially acceptable to choose NOT to have children meant people made very conscious choices about if/ when to have children and how to raise them in the best way.
Just a few thoughts ...