MacOS now has Hindi available as of the High Sierra release! I’m wondering if they’ll add other Indic languages in the future. I’d still like to see them adding Welsh, Irish, UK English and Canadian French user interfaces down the line, but Hindi is a major step forward for them. I think much of the inconsistency with MacOS localisation compared to iOS and even watchOS comes from the allocation of resources at Apple HQ; as the iPhone is its top-selling device, most of the language work is done over there.
iOS 11 has considerably expanded its accessibility options in comparison to previous versions.
The Glyphs Mini font-editing app has a lot of stray English text in the French localisation, particularly in the preferences window. Most of the text isn’t even in French, which looks kind of careless. I’ve tweeted at the developer to see if he can fix it in a future update. Remember to be thorough when translating your apps into new languages or variants of a given language.