That said, I am afraid the Internet is a game changer here. I didn't have Internet access since... ~13, AFAIR, and even that was over dial-up. Given how today there's infinite amounts of brain crack streaming down the ever wider tubes, I fear a kid left in front of an Internet-connected computer will never get bored enough to start tinkering.
So I'm all for lots of unsupervised computer time, but for my future kids, I plan to not introduce Internet access too soon. Mind you - I'm not worried about the content (porn and other usual scares), just about it being like more addictive TV.
Are you sure? What about people growing up with cars, curious about what goes on under the hood from childhood, with references available on how they work, that they can connect to what they've seen themselves? Maybe this gives an edge over those whose learning started later?
Human technology is a long ladder of improvements one generation makes over the one prior. It's not obvious that stone age toys are the best preparation for contributing to the next step of the ladder.