My husband lives with a chronic neurological pain syndrome. No gift there - not directly. But . . . even he would say that having lived with his pain for almost 35 years now, he has acquired an ability to prioritize, to appreciate, to adapt, to persevere, in ways that have changed him in positively. It wasn't the pain itself that was a "gift," but the changes along the way that have gifted him with some really positive attributes that he might not have acquired is he hadn't had to deal with his challenges.
It seems like the oversimplification and misuse of such a trite phrase is probably where most people take issue.
I've lived through some horribly painful experiences myself, and I would never say they were somehow okay because they made me stronger. Never. I would say the journey following the painful experiences eventually led me to a much healthier me (but that was a slow and painful journey in itself).
I don't think everyone necessarily reaches that place where they can see or live beyond that original or chronic pain (physical or psychological). Some do, but it is not a quick process that some trite phrase will automatically send you through, and people who speak in idiomatic expressions and aphorisms tend to come off as condescending, impersonal, unsympathetic jerks. LOL.