> I had more or less unrestricted internet access since the time I was able to use a computer, but it feels like it wasn’t overly harmful

I have the opposite experience.

  - I've been addicted to pornography since I was 12.
  - Late computer use caused me to never get enough sleep.
  - Programming early started my career, but it also isolated me socially.

YouTube and Tik Tok scare me; as a grown-up, I can still waste hours just swiping and swiping. I suspect that getting this behavior early on will make you more docile. My siblings raise their kids with tablets, and it impacts their learning ability and sociability tremendously.