> Japanese programs aren't globalized and already rely on the system being fine tuned for Japanese
Right, because unicode-based systems don't work well in Japan. E.g. a unicode-based application framework that ships its own font and expects to use it will display ok everywhere that's not Japan. So Japan is increasingly cut off from the paradigms that the rest of the world is using.
Custom fonts are often a mistake for any language, especially google fonts often look wrong. Due to this browsers often have an option to force usage of system fonts and set minimum size to improve readability.
Right, because unicode-based systems don't work well in Japan. E.g. a unicode-based application framework that ships its own font and expects to use it will display ok everywhere that's not Japan. So Japan is increasingly cut off from the paradigms that the rest of the world is using.