That's what I don't get about GOP strategy here. They have to know their position on healthcare is a political loser and is playing right into the hands of the AOC/Sanders crowd. The public sees an ACA that is objectively failing many people, and so why not Medicare for all? If the GOP are going to oppose any efforts to make the existing system work, then why not burn it down, and replace it with the far left alternative?
This speaks to wider problems than merely healthcare - or even choosing the right issues.
Firstly they've painted themselves into a corner: in order to keep getting reelected - even in safe sets - they need to keep sucking at the corporate teat. Without the donor money they run the risk of getting primaried by someone more extreme (safe seats) or losing to a Dem (vulnerable ones). Sometimes both. So to keep that money coming in they need to have policies that favor the donors, in this case large insurers or corporations seeking tax cuts. These both negatively impact ACA. Yet to keep the sick voters, of whom there are a lot, they must pretend to care about affordable healthcare. So they must sell themselves as having a plan, looking for an alternative or against any cuts to medicare/medicaid, while actually doing the opposite. They will get caught sooner or later. Many of the base hate libs enough to let it slide and lose their healthcare, some will embrace cognitive dissonance and accept the given excuses by their GOP reps, but not all will be fooled. So they must continue the policy of selling one platform to the base, but actually delivering another for the donors.
Because the party has been hijacked by both special interests and grass-roots right wing partisans the average conservative GOP congressman is stuck squarely in the middle.
Now because they can't fool everyone all the time, common sense would dictate that they find more appealing policies and run on those. But the donors will strip them of backing and a more right-wing challenger can dismiss them as socialist, so that's really risky. Most feel they have very little wiggle room. if they run on a more moderate policy, they might lose to Dems who do better on healthcare votes; they might get primaried by a rabid Trumpist who then goes and loses the seat anyway for dialing up the crazy.
What of changing demographics? Well that's where we come back to the other side of plan A. there was never a plan B (to deliver the services people need), but there was a safety net built into plan A: voter suppression, gerrymandering, propaganda. If your policies simply don't attract a wide variety of voters, but you're unable to change those policies, then stop such a wide variety from voting. Voter suppression in all its forms is now the go-to weapon of the GOP. That can't work forever either unless it becomes even more prevalent and far-reaching, but for the next cycle and the one after that - as far as the embattled GOP Rep or Senator can see over the smoke of the Trump presidency's dumpster fire - it is their only option. Keep running policies that people won't vote for and stop more people from voting.
So as I said this is way bigger than ACA. If that was the only problem they could just make a better plan. But the problem is serving two masters while holding on to power. They fear that right wing voters and donors will punish them if they become more moderate, and that it's easier to suppress any voters on the left than to win them over.