LOL, Obamacare was Mitt Romney's (Republican) plan from Massachusetts. The Dems really wanted a single payer option, ie Medicare for all, and the Republicans fought against that.
Bottom line. The Republicans have no plan to replace the ACA with anything that will address the problems.
And the problems are many.
1. How do you pay for the very sick? You need the young and healthy to be part of the insurance pool.
2. How do you pay for outrageous pharma prices? Allowing Medicare to NEGOTIATE prices would have saved tons of money but the Republicans didn't want that since their buddies in the Pharma industry lobbied that dead.
3. How do you cut costs, currently 18% of GDP to 10% like single payer countries with a profit driven system like the US's.