Yes it likely would be far better as a single payer system. it was conceived as such and only when it was clear that it had no chance of passing in that form, compromised into what it is today. Which still had some very good benefits such as inability to completely deny for pre-existing conditions, formalizing plan tiers with standard levels of coverage, limiting out of pocket maximums, and subsidized premiums from a federal marketplace for those that are income-limited. Also employer mandate for employers over a certain size, and a more toothless individual mandate which Trump later repealed.
Many of the things people dislike about it are precisely because of the compromises made and because it is not single payer. the whole concept sort of hinged on single payer.
Forcing extra coverage and limiting out-of-pocket maximums without any other regulation/control over private healthcare insurance industry naturally leads to premium rate hikes. Subsidizing insurance premium costs for lower income by having the federal government cover some portion of the bill naturally leads to premium rate hikes. Repealing even the individual mandate means less people in the healthcare system to pool risk which naturally leads to premium rate hikes.
About the only way to fix these fundamental issues is something like much more intense govt control and regulation over health care industries, such as widespread price controls like what medicare uses. This would probably leave not much purpose for most of the health insurance industry. It would be a difficult and disruptive transition to be honest no matter how much I support the concept. I think this is what proponents in the past have failed to acknowledge. There would need to be some wide reaching support plan for everyone displaced and not "maybe they can become coders"
On the other end, detractors of single payer say things like "I don't want to pay for somebody else's illness" without perhaps realizing that that is exactly what they are doing with private health insurance now. Private health insurance is pooled risk - your premium is paying for other sick people, and if you ever get sick other people will be paying for you. Private health insurance is just a less efficient method than single player because the pool is smaller and lacks any power price regulation.
America has a real problem with accepting direct subsidies that help literally everyone. People falsely assume it is a zero sum game and our great grandchildren will have to bear the cost or something. Myths when things can be paid for largely by cost reduction
The populus is willing to let subsidizies for the poor, such as the Federal Student Loan program and the federal ACA healthcare marketplace slide. But these are implemented in the worst possible way and benefit the private companies more than the end user, with the govt picking up the portion of the tab that essentially the free market couldn't naturally support. In both cases it leads to spiralling increased prices. I'm of the opinion now that such subsidies should only come with some form of price controls, since it isn't really free market anymore. Or just don't do the subsidies this way.
The two issues I bring up are somewhat interlinked, with medical professionals taking out exorbinant amounts of debt due to the extremely high cost of education. This leads to them demanding higher salaries to pay back their quarter million dollars or more of student loan debt, which trickles back in some form to healthcare cost. The high tuitions being propped up again by a federal subsidy program that encourages colleges and universities to raise rates.
America is also a very litigous society and doctors and providers need to deal with potential malpractice suits, and pay hefty fees for malpractice insurance from what I understand. I'm not sure what the ACA did to address this aspect if anything, but it would be something else to look at in a single payer system.
I think the most feasible idea I've heard so far was Bernie's plan for "Medicare for all" which involved gradually lowering the age of eligibility of the Medicare program (which people seem to know and love) over some period of years. Medicare also has limits in place for what they will pay for certain services and prescription drugs etc.
For complete clarity, even private health insurance has limits on what they pay too. You'll see this discrepancy on any medical bill between what the provider billed and what the agreed rate the health insurer will pay is, often several times lower. And the provider just accepts this lower agreed amount and says, "Mmmkay, I guess this is the bill now" So both private health insurance and Medicare do use some form of "price control" already.
The difference being, if you happen to be uninsured and get the same bill, you have little bargaining power to negotiate that same "agreed rate"
So again I support an idea like "Medicare for all". But it comes with some uncomfortable truths that I think need to be acknowledged and planned around if such a transition were ever to occur, and if it is attempted it is very important not to go "halfway" and compromise again or we might end up in an even worse mess.
If there remains some small very pool of private health insurance as someone's sole primary coverage, it will likely become unstable and have skyrocketing rates. I think though that the age reduced "Medicare for all" rollout would safeguard against this, since the last age group to be included would be the youngest and healthiest. But it would be difficult to guarantee in todays political climate that the rollout could even continue unhindered, as it would likely span presidential administrations and certainly midterm elections in terms of length.
There can still be a place for private insurance with a single payer system, and that would be supplemental insurance. This would be an option for coverage of more optional procedures, or potentially reduce wait times etc. I believe several european countries have supplemental private plans on top of the public option.
I'm not a professional in any healthcare industry, but I have had people close to me die due to health complications while being either uninsured or underinsured. I really think something like "Medicare for all" or other single payer system would have greatly extended their lives. As it was they would put off visits to the doctor unless it was an emergency due to the bills, despite having ongoing health issues that should have been carefully monitored.