Agreed. Currently, it is a very manual process that is relatively theme-specific and requires careful SEO effort, etc.
The configuration is not impossible, but mostly tedious and inaccessible to most content creators (e.g., those who are not technically inclined). That’s exactly where Ghost can play & make the biggest impact. It should take ownership of this development, especially as it is commonly requested.
IMHO, setting two locales + tags should be enough, with an online editor for the soft-coded text strings. Most bilingual content creators can translate our content ourselves, but needing to become Handlebars / Ghost devs or pay again (Ghost Pro + theme + translation up-keep) for theme-specific development (+ support for future breaking changes) just to segregate content properly (SEO, HTML tags, pages, strings) is not an insignificant barrier.
EDIT: to be sure, this is from the perspective of Ghost(Pro) customers. Others who self-host Ghost aren’t quite in the same boat, IMO.