This chart is easier to understand if you make the following substitutions:

• Toy Lang --> high level language (except brainfuck really is a low level toy language)
• System Lang --> low level language
• Obsolete Lang --> old programming language, regardless of obsolescence status
• Nu Lang --> newer programming language

After understanding this construction, I fail to find any humor in this.

Why is ECMAScript here and not JavaScript?

Among other things, “JavaScript” is a trademark of Oracle.