Let's be honest about what this really means. First, in spite of seven solid years of complaining about the ACA, Republicans have never had a replacement plan. Their endless harping was just political haymaking, without substance. When Trump surprised everybody, including House and Senate Republicans, by getting elected, they had to scramble to turn their empty posturing into some kind of legislation. But they couldn't do it. They couldn't even get the numbers at the bottom of the spreadsheet to balance.
A second take-home lesson is that this failure is entirely the fault of Republicans. They had time, years in fact, to work this out and align their votes. And as of January they've controlled the White House, the House, and the Senate. While Mr. Trump and party leaders have tried to paint Democrats as being obstructionist, the fact is that the practical differences on the ACA and its repeal and/or replacement lie between Republicans and Republicans, not between Republicans and Democrats.
The third take-home lesson is that Mr. Trump's campaign bluster was never more than empty hot air. He promised Americans coverage for all, coverage that was better and cheaper. He didn't deliver. Realistically, he never had the slightest inkling of how to deliver on any of it This was, of course, painfully obvious to more thoughtful American voters even during the campaign, but was sadly irrelevant to Trump voters.
Mr. Trump and Republicans in Congress now have a huge opportunity, although there is reason to doubt they have the mental wattage to take advantage of it. They could save the Affordable Care Act. It works in broad outline, and needs some propping up in places, some additional funding here, some tightening of regulation there. While funding and regulating -- rather basic functions of government -- are things Republicans are philosophically opposed to doing, they could make a pragmatic choice for the good of the American people as a whole.
The alternatives to saving the ACA remain terrifyingly cruel. Make insurance unaffordable to anyone with a pre-existing condition. Let insurers offer sub-standard policies. Lock healthy people who get sick out of health care. In other words, insist that health care in America remain the inefficient, expensive, and inaccessible mess it has been for decades. "Let the ACA fail" and "Repeal then Replace" mean the same thing. They mean ordinary Americans will suffer because Trump and the Republican party could not deliver on their promises.