That would obviously be Javascript. A toy language no sane person would use willingly but just powerful enough to demonstrate the sheer minimum of what a computer can do. Yet its adepts are know-it-all gurus who will never, ever, need another language again. Hence the preoccupation with re-implementing every piece of software that has ever been conceived, in Javascript. </rant>

The subset of C/C++ you see used in typical Arduino sketches seem to be what's evolved as the replacement.

The kids I see using Arduinos seem roughly like the same set of kids that would have had an 8-bit home computer in the 80's, and actually spent any time programming on it.

Oh no no no. If we do a 21st century version, we'll throw in all sorts of opinionated CS jerkoffery into it, and then it will look just like everything else--where we have to pass through three different toolchains before we can even think about running something.

Bicycles are already pretty good just the way they are.

Microsoft released Small Basic in 2008-2015 https://en.wikipedia.org/wiki/Microsoft_Small_Basic though a cynic might say that it's just an on ramp to VB.Net

Python is pretty much taking over as the go-to beginner programming language (see what I did there?).

However my daughters are learning VB.NET at school for her GCSE Computer Science (UK). It's a very capable language, if a little bit verbose and clunky, on a modern runtime and with excellent tooling. Until recently they were using Visual Studio for Mac, but we got my eldest a Windows 10 laptop for Christmas so now she's on 'real' Visual Studio. They're both very good though. It's quite something to watch her debugging code by setting break points, inspecting variables and such.

Hypercard has a modern implementation called LiveCode[1] that might be a good starting spot, but is definitely not as accessible as the default installed Hypercard on a System 6/7 machine.

[1] https://livecode.com/

Also Swift has 'Playgrounds' as an iPad app or online http://online.swiftplayground.run/