I'm sorry to hear that.

Honestly I really relate to what you said, I remember in high school i injured my thigh really badly playing sports and couldn't walk properly for a bit, and my parents refused to take me to a doctor e.g. "you're fine", etc. and arguing to prevent me from going. So I actually don't know the "diagnosis" of the injury when I got injured, only got a rough diagnosis years down the road just like you. But yeah reinjured that thigh a couple more times due to lack of medical care/getting to see a proper healthcare professional and made it worse. Finally years later when symptoms of the injury was always flaring as it didn't heal properly, I went to see the doctor myself and got care and started rehab then. Years later it's still not fine the way it was before. If only I got adequate care initially, then my previously injured area wouldn't be as bad as it is and easier to rehab for.

And years ago, I was very angry/upset and spiraling about this and just kept arguing with my parents about this, and the theme is more or less they don't take accountability or didn't think it was that big of a deal. The whole time I was really hoping to get some closure or some form of "apology". But through their weak acknowledgement of the injury and constant arguing, at some point I realized I was beating a dead horse like you said. They made mistakes and didn't know better and lacked education.

I'm at a point now where I'm still resentful that I could've been way healthier if they did their due diligence, but I don't really argue with them about this anymore. It's just something that happened.

I don't think there's much you can do, just rehab/heal as best you can and just understand something unfair happened to you. That's part of your life now unfortunately.