What advantages do block programming environments like App Inventor have over high level programming languages like Python or Java?
Developing complex software is completely different from writing small programs.
Complex individual systems are usually elements of complex ecosystems of software and hardware platforms, interfaces, languages, and even extra-computational factors. In creating those kinds of systems the choice of languages that use visual metaphors would probably be detrimental, not beneficial, and that is why professional software developers are happy that the languages they use are "spartan".
On the other hand, if your intention is to reduce the learning curve for begginers that are not going to be professional developers of any kind, then you can begin to talk about the benefits of those "soft" languages.