"It isn't to have low-risk people subsidize high-risk people. "
That is EXACTLY what it's about. That's how premiums can be affordable. And quite often low-risk people end up with some illness which costs huge amount of $ to treat.
"They may find the higher premiums unaffordable, but that's not the same as being told they're absolutely uninsurable."
Yes, it is the same thing.
I agree with the collusion argument. As long as docs are the higest paid profession and drug prices are unpublished we are being had. The fundamental fallacy is that poor people cannot afford servants, but government programs pretend that they can.