On the journey to becoming a productive member of society I had to compartmentalize my inner child.
During my early schoolboy years, he waited patiently for the school day to finish so that he could finally resume his creative and playful pursuits.
As the education became more involved, he had to wait a little longer because of homework.
In university, the complicated assignments, group projects, and late night study sessions meant that he would often not get to let loose until the weekend.
The full-time job, commute, technical projects, work politics, and other adult responsibilities really did the biggest number on him though. Sometimes he would go without playing for weeks, or months at a time.
Today it's as if my adult mask has adhered permanently to my face and I can no longer access him at all.
I don't really have an inner child. My childhood sucked. I have nightmares about feeling angry and scared and trapped like I did as a child. My adulthood just keeps getting better. I'm learning to enjoy life and the world for the first time, and I'm a more productive member of society for it. What you describe is totally alien to me.
It's also an important trauma processing technique. If you had a shitty childhood like us, it's called reparenting instead.
Similar. Riding on rollercoasters, watching wholesome cartoons, and reading good fiction don't feel childish to me, they just feel like well-deserved fun. Why associate that with childhood, when childhood lacked freedom?
You could totally work with your inner child on that basis. Obviously don't have to. But just imagining this little version of you and the hardship they had to endure, thinking about what they would have needed from an adult, and imagining yourself being that adult for your imaginative younger self - that would be very much in line with the idea of the technique.