They've been trying to tell us they have this secret plan since the ACA passed in 2010. Fifteen years of swearing up and down that it's some great plan that will help everyone, maybe including poor people if they think it'll help convince anyone but definitely including insurance companies and pharmaceutical giants.
The problem is, the ACA was already their idea. The 2006 Massachusetts law that he proposed and signed into law as governor was an early version of Obamacare, including the Individual Mandate and a penalty for businesses that didn't provide insurance to their employees. It was a stopgap measure to overhaul the system so that patients wouldn't use the ER for health care and run up huge unpaid bills when they could just pay for the care from the correct provider; but unintentionally, it also got 98% of Massachusetts residents insured.
But by the time Romney started campaigning for president in 2012, the GOP had already started moving dramatically to the right, to the point where this lukewarm, milquetoast excuse for a solution was seen as radical. And since the GOP can't risk doing something that will reduce their voters' hardship (because paradoxically then they might stop voting for them), they are terrified of coming up with anything that might actually help.