Multi-lingual support in WP has always been plugin territory (and probably should remain that way, to control core bloat). A few years back there was this project, led by Simon Wheatley, to give multi-lingual plugins (all bad/difficult implementations) some kind of core infrastructure, introducing a core language field, that would identify content language in the database (https://multilingualwp.wordpress.com/). It’s not an easy task, I know, but certainly this is an area where Classicpress could lead the way to a better multi-lingual content management. And a need for the enterprise market.
This is actually what project Gutenberg is about in a certain phase (I don’t recall the precise phase). I think it is planned for the coming year in WP?