To replace the ACA, Republicans in Congress have proposed a bad plan with little of the preparation usually devoted to legislation. A going theory is, perhaps they did this on purpose, so they can lose the battle without having to actually fix anything or take on new problems, blame Democrats in the Senate, and move on briskly to 'tax reform' and other issues.
Ezra Klein writes, "So do I think the GOP plan is built to fail? I don’t. Washington is always more Veep than House of Cards. But I do think Republicans went into this process believing that failure was likely.... They decided that if they were going to fail at this, they were going to fail fast, over the course of a month or two, not waste a year on the project."
Which is sensible, if you think government is essentially doomed to failure, anyway. The free market, small government crowd hasn't had a vision of a functioning, workable system since Newt Gingrich's Contract with America. If oversight, regulation, and taxes are all bad as a matter of principle, there's very little role for a federal legislator to play.
This is so, without worrying about whether or not Paul Ryan can actually do math, or if his ideals are at all fact-based. The answer to both is 'no', but it doesn't matter. Republicans don't need to be competent to fail at a task they have no intent of accomplishing.