I loved Scratch as a kid and got really deep into it. Not sure if I could call myself a "success story" but it did get me much more comfortable with programming!

Before Scratch I think the two biggest barriers in my childhood programming experiments were 1) Remembering all the different syntax and function names, and 2) Being bored by the basic CLI programs that all tutorials started with. Scratch helped with both of those. It had a palette with all possible commands available to you, it was impossible to make syntax errors, and it was visually-oriented so I could dive right into making games. Lowering those barriers helped me learn how to structure code in a fun way, so when I did eventually go back to the "real" languages I felt much less lost.

I also remember really loving the social features, getting comments on my work, and collaborating with people.

I'd love to see more experimentation in this area, there's definitely potential for a more modernized educational language that builds on these ideas.