Regarding Java and C#, I am stunned by how good are IDEs now. To be clear, when I say IDE, I am specifically talking about a tool that enhances the edit-compile-debug cycle. Compared to 20 years ago when I wrote C, C++, and Perl, the IDEs were mostly terrible, except Visual Studio for Windows. The majority of my development cycle was all terminal-based: vim to edit, make to build (C/C++ only), gdb/perl -d to debug. Hoi, awful. (And, I still enjoy those all three languages!) As mega-corp computing slowly migrated to Java & C#, my productivity has increased dramatically. I guess at least 2x, if not more. Yes, some of this comes from how forgiving a modern VM can be (NullPointerExceptions, debugging, etc.), but a lot can ascribed to the incredible ecosystem of IDEs.
Regarding JavaScript, in the context of a modern web browser, high school students (in almost any country in the world) can easily Google a little bit, read some blogs, and then start GUI programming. And this doesn't require expensive, licensed software, like Delphi 30 years ago.