To be honest, that thing is scary even for me as fit adult male. One little mistake and I could seriously hurt myself. Same for the children. I would be very uncomfortable letting my own child climb around on this to be honest. I would probably let it, but feel bad the whole time.
They are significantly easier for kids to climb on than adults. And kids generally have a good sense of their own limitations. Most playgrounds nowadays are deliberately designed with different levels of difficulty, which kids self-select on.
As a parent of two kids and a teacher, they don't make me nervous.
I used to play on that kind of thing in my childhood. A child can (and probably at some point will) fall down, but usually not from the highest point, but rather while climbing. Also, there's sand underneath, so the landing is somewhat softened. That said, it's still easy to seriously hurt oneself on that, but I was aware of that as a child and acted accordingly.
