It's much safer to be a kid now than when I was growing up, but the news makes it seem like it isn't. I would let my seven year old walk to the park by herself, 1/2 a mile away, if I wasn't afraid of having the cops show up.
When I take her to the park now, I let her play on the structure about 100 yards away, within my line of sight. And still adults will come up to her and ask her where her mommy and daddy are.
My nephew is not yet four years old, so he's probably still too young to be outside playing on his own, but I fear he'll be in the same boat as your daughter in a few years, unable to do anything outside of his parents' line of sight.
I think you’re right: in the past, each kid was much less work than they are today. The difference is that you also used to have 6 of them, and used to expect that not all of them might survive to adulthood. This is clearly not acceptable approach in today’s society.
Around the 70s the workload ratchet started going up, with each decade adding more and more restrictions. Look at stranger things, today it's a bit iffy to let 12 year olds go out biking by themselves to see their friends. In the 80s you could!
[0] https://www.nytimes.com/2018/08/02/reader-center/free-range-...
Your 7 year old would not be asking for you to endlessly watch her cartwheel and interact with her out of bordem. They would be out playing 24/7 in the local forest, come back for food and boo-boos, be back before dark and be in bed a couple of hours after dinner / night time with an 8 or 9pm sleep time and a 6am wake time.
Kids were not meant to be a lot of work, our society makes them a lot of work.