This is a good list. The default user experience for Perl 6 needs to be dramatically improved.

Developer ergonomics matter! Yes, when you run 'python' you get cpython, and Java is probably hotspot vm or openjdk or something (but Java is not a good example of developer ergonomics).

Rust is one of the best examples here -- adoption is being driven by the ease-of-use of the entire toolchain, including the package manager and things as small as human readable compiler errors.