I agree that children are not necessarily more immature, but they are certainly more mollycoddled.
At age 11, I was still happily playing with my barbies and baby dolls. This was my first year of secondary school. My friends played with them too. My (almost) 8 year old daughter wouldn't play with them. Yet at the same time, I was allowed to play in the street from age 4, go to the park / shops whilst in juniors and walked home from school alone when in year 5 (this involved a 10 minute walk and crossing two main roads). By the age of 10, I was allowed to catch the bus into town and meet my friends. By the time I went to secondary school, my mum went back to work and during the school holidays I was expected to look after myself all day every day.
I believe in giving my children this sort of childhood. I am (and have always been) fiercely independent, and love my freedom. I want my children to do that too. Yet some of the comments I have had from other parents sometimes make me sound positively neglectful. Here are just a couple of examples...
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My (almost 8) year old daughter is able to make herself a cup of tea / coffee and often brings us breakfast in bed at the weekend (bless her!) I said this to another mum with a child the same age and she replied that she would not let her child use a kettle in case she burnt herself. She then went on to say that she wouldn't even let the child play downstairs whilst she had a lie in, incase the 7 year old child wandered off. I didn't like to admit that I expect my four year old (almost 5) to get up, make her own breakfast (cereal) and play until we get up 
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My DD had a friend over to play and they wanted to go to the swings, on our estate (about 2 mins walk, on the next road to ours with no main roads to cross - small market town so very safe). I asked the mother of this child if they could go (the child is 9 going on 10) and the mum wasn't happy. I had to take them to the swings.
I think there are a lot of reasons for it though.
Culturally things have changed, children are expected to be protected so much more. My daughter is in year 3, and I would like her to walk out of school alone to meet me at the end of the path leading to her school, but the school won't allow it, they insist a parent has got to come to the school to collect them.
I agree that the litigious culture means that people take less risks.
I think there are more expectations on parents, and more nannying from the state - for example, the NSPCC now say children shouldn't be allowed to play in the street before the age of 7/8, and not left in the house alone until the age of 12. Hell, by that age I had been playing out in the street for 4 years, and was looking after myself all day, every day of the holidays! I also had a part time job from 14, earning my own money. You don't see that any more.
Then there's parental paranoia. People keep telling me that 'things have changed' and 'its not as safe anymore'. I'm not that convinced that so much has actually changed. Yes there are more cars about, but that is all.
Hmmm, that went on a bit. Sorry 