These are all excellent and effective strategies for most human brains, but just not all. Very difficult to deal with teenagers aren't solely a product of ineffective parenting - it's not a 100% preventable problem. There's neurodivergences like ADHD or ASD, hormone-affecting conditions like PCOS, and more severe behavioural health problems like schizophrenia - these are all incredibly difficult for well-adjusted, materially comfortable adults to deal with.
I definitely agree that not abusing kids will help reduce the amount of un-deal-with-able issue that those kids have as teens, but you can't just wave a wand and make abuse stop. Unless we as a society allocate a large amount of resources to break cycles of abuse and eliminate the kind of poverty in which abuse festers, there will still be noteworthy amounts of childhood trauma.
I think some kind of state-run teenaged-care facilities is the best, most realistic option. It's still a lousy option, but there would be more accountability than the private-run troubled teen industry, which is itself an abuse factory.