That's still too many steps - the trouble with bi/tri-lingual life is you often interject words (places, addresses, proper nouns) in the local language into sentences in any of the other two languages.

Constantly opening and closing settings dialogs gets on your nerves in the long run.

Adding a language to your phone (once) is too much work? Or is a “button” press to swap out the keyboard too much? I don’t understand.

I use English, Swedish accents and Russian with no issue. :s

When I was on android, I could type a message in one language, change who I was talking to, and start typing in another, and the autocomplete would immediately know I had changed language. iOS constantly corrects my first few words before realising. And sometimes the keyboard sets itself to a non-multilingual keyboard.