A lot of the responses here seeking a modern alternative to this experience seem to be focusing on hardware. In a way that's not surprising but I think it's a bit of a shame. That's because I think we have a platform today that can rival the ease and immediate feedback of those early computers: the web browser. There are probably a couple things needed to complete the picture.
1) A nice basic library that can serve as an immediate stepping stone to the UI. There's probably some out there already that are very beginner friendly.
2) Some kind of REPL/IDE like browser extension to make it easy to dive in right away. Something a bit easier for kids to wrap their head around than the developer tools of today, but also incorporating a basic editor so they can edit in place, save files etc.
I'm not really sure about the form of (2) or how vital it is, but it certainly wouldn't hurt.
I'd second this suggestion. Another great 'feature' of this platform is that it's trivially easy for the learner to share his/her creations with friends.
1) A nice basic library that can serve as an immediate stepping stone to the UI. There's probably some out there already that are very beginner friendly.
2) Some kind of REPL/IDE like browser extension to make it easy to dive in right away. Something a bit easier for kids to wrap their head around than the developer tools of today, but also incorporating a basic editor so they can edit in place, save files etc.
I'm not really sure about the form of (2) or how vital it is, but it certainly wouldn't hurt.