Our kids write well because they spent time translating from another language, French, German, Greek, and Latin. But Latin is most useful for translation exercises. It teaches you the structure of the English sentence like nothing else.
Translation also makes you think twice about your word choice and makes you learn distinctions in English. That contributes to fluency.
Reading is passive. Writing is active. Translation exercises promote active fluency. But, yeah, if you can’t read, first learn to read.
Actually, translation does more than just that.
There are plenty of people who speak two or more languages fluently (I'm talkin' near-native-speaker fluency here), yet flounder when challenged to translate, e.g., a legal text from one language to another.
Having grown up and gotten a degree in the U.S., then spending the remaining 2/3 of my life in a foreign country, working as a court-appointed interpreter and technical translator, has given me an appreciation of that fact.
But, of course, you are speaking here of mere "translation exercises."
Regards,
two yrs of classic Latin taught to me by an old old nun....didn’t do very well in it...but it does give you a lot of info about the formation of language....