ACA doesn't fix these problems. Instead, it forces people who use medical care and insurance responsibly to subsidize those who don't. Furthermore, it makes it hard for insurance companies to signal the cost of poor choices to people through their rates. That does ensure universal coverage, but those are exactly the things you don't want to do if you want to control costs and improve public health. Americans will get poorer, sicker, and fatter as a result of ACA.
But "responsible people" were already subsidizing those who aren't. It was just done indirectly and very inefficiently, and with huge gaps in coverage for legitimate illness that otherwise "responsible people" found themselves not covered for.
I see what you're saying, and I agree that the ACA is not an ideal solution. It was only adopted because it was almost entirely Republican-drafted and Democrats assumed that would mean they would get at least some support.
The whole concept of "health insurance" is a bit wonky, because you can be dropped from your coverage whenever by an insurance provider. Insurance is designed to spread the risk of single-event large-scale losses, but health is almost never that. Obviously, there is the catastrophic accident scenario, but that's relatively rare in our hyper-safety society, so the bulk of health issues are chronic and/or terminal.
Having an intelligent discussion on how to deal with chronic illness is a serious concern.
Obvious, systemic issues such as obesity need to be addressed, but I'm not sure that "your insurance will cost more when you're 40" is a sufficient, nor really even a very useful signal to "don't eat ice cream for dinner" to some random chubby 23 year old.
So, on that, I reject the idea that "signaling bad behaviour via the future cost of health insurance" is a relevant marker for the value of a health program.
There are some programs in the world (like Japan) where the government offers universal coverage, but only pays something like 80%. You can buy private insurance to cover the remainder, or you can eat it. People under a certain income get 100% regardless and that moves up on a graduated scale. This gives them incentive to avoid unnecessary procedures, but still offers universal coverage for catastrophic injury and the poor.
I don't think any changes to the healthcare or health insurance system will fix things like obesity or smoking, frankly, because most humans are inherently REALLY bad at planning. So I contend that we can virtually dismiss the "changing habits via the threat of future cost increases" as a viable tool to change public behaviour.
Given that, what alternatives are there that don't completely suck, other than a public-payer system? I'm not sure I see the argument outside that.