> nobody reacts well to e.g. neglect or mistreatment
Maybe, but some people react by becoming stronger and some react by breaking down and failing. Regardless of other effects like depression, anxiety, paranoia etc., being stronger tends to sound better, even if it has other trade-offs, you know? If you ended up weaker then sometimes nothing can convince you that's what was best.
I don't think "weak" and "strong" are useful in this discussion without defining them carefully. The way most people seem to get through these things is by becoming more thoughtful and emotionally mature. This is what is generally meant by "weak" in these conversations. "Strong" leads to pills and bottles and painful deaths trying to fight the feelings down.
> being stronger tends to sound better, even if it has other trade-offs, you know?
That feels like a tautology. From context, you've defined stronger to mean better. So of course in that case stronger is better. But in reality stronger isn't always better. If you come to a chess match being able to bench more than your opponent, are you better at chess than them?
If there are tradeoffs, and there are always tradeoffs, then you can't actually say stronger is better. The neglect of your parents might make you more independent and you might find that helps with your work life, while at the same time it makes your personal relationships harder. Which of those do you happen to value more?
Which is not to say you can't personally find value in and appreciate even the negative the experiences that made you who you are. But you can't say something like: neglect is good because it makes people stronger. It could be true for your life and what you value, but it's not objectively true.