“It was. The Ministry of Magic’s entire supply got broken in the battle.
(‘?’ ??? ?)”
Not relevant to anything taking place before then. And it was in ‘??? ?
Whilst the Battle at the Ministry indeed took place in ‘??? ?, the fact that all the time turners had been destroyed was revealed by Hermione in ‘??? ?, in response to Ron’s query as to why they didn’t just get one.
“and before that people were very wary of messing with time, due to various unforeseen circumstances (‘?’ ??? ?).”
It doesn’t make sense to be worried about unforeseen circumstances because any unforeseen circumstances would have happened already. Unless you say that something already happened but no one knew about it yet and it only happened because you will go back in time, in which case by not going back in time it will not have happened.
And as regards the effects having already been felt, it says ????? in ‘??? ? that one of the dangers of time travel is that you might get cursed by your past self. This would mean that whilst the sequence of events up to now would perhaps remain the same, but ???? ?????? things could change. For example, the one using the time turner would be killed and be dead in real time from here onwards. An example of this would be Harry getting killed outside Hagrid’s hut, and not returning/dying in the closet where he used the time turner (the book doesn’t specify what happens in oresent time when you use the time turner, if you disappear or remain in a state of suspense, or whatever).
Granted, this does not explain the time paradox in it;s entirety, but does at least answer why there is only one (known) instance of complete time travel in the books.