You don't know what your sister's experience truly was without being her.

Though I do agree with you that negative emotions are human and that we shouldn't necessarily fear them. Sometimes you'll be in situations where you'll be uncomfortable and upset, and you're going to experience things you don't like or you'll have to do things you don't want to do. That's part of the human experience and dealing with it is an important life skill to learn, especially for children.

Again, I'm not talking about trauma so grave you actually need therapy to get you out of your funk, like wartime memories or terrible accidents.

The very strong tendency of therapy is to assume the latter despite evidence of the former.

Society has completely lost its ability to deal with any personal/spiritual/psychological/social issues outside the context of professional talk therapy.

Let me introduce you to toxic positivity:

https://en.wikipedia.org/wiki/Toxic_positivity

I think its great we can talk about feelings, and let them out, we as a society have absolutely gotten better at being able to express...(if politely) but in terms of help and support when fixing that's a bit lacking.

The therapy thing seems a very USA/entitled thing, just pay to have it fixed. Most don't have that luxury. But the bottom line is you may need to work on how you handle things. I know its easily said but anger and resentment can be used to fuel you to do good. Just remember there are people who care, even if its just another internet buddy.

Correlation and causation shouldn't be confused for the other.

Therapists are a major source of learning why, when, how these emotions come up and give you techniques to deal with them.

I may be wrong, but here's my theory: she and I went through the same hardship: I allowed time to let the memory fade away in my brain (it wasn't PTSD-inducing hardship, mind you) but her therapist never let her forget. And now decades later, she's all kinds of messed up and I'm not.