> Where is it now? I'm not sure (and I would love to know) how kids these days are building things that are able to compete for valuable attention span.

I'd say it's videogames. I got into programming through glitching games, then scripting games, then programming games. I know a lot of other people my age (mid-20s) who had similar experiences.

Look at kids making various contraptions in Minecraft -- and look at how many of them go into the modding scene.

I don't think that tinkering experience has been lost; people just forget what a small fraction of the population was interested in this stuff in the first place.