/languages/ folder missing in default themes

Themes and plugins on wordpress.org don’t need a /language folder anymore. The translation is made via Glotpress on https://translate.wordpress.org/. Glotpress parses the files and you can start to translate. The translated .mo and .po files get automatic updates, if a translation string changes. They are stored in /wp-content/languages

If you don’t host your Theme or plugin on wordpress.org you need a /language folder. More infos in the handbook: https://developer.wordpress.org/themes/functionality/localization/