About half the field of Republicans who ran in the primaries would have defeated Hillary and would have had no problem repealing Obamacare. This argument that Trump was the only republican who could defeat Hillary is total bunk.
Any other candidate would have lost. Why: trump found a new set of voters. The republicans have sold their soul for those voters (and still lost the popular vote despite Hillary being a weak candidate). now the party is an incongruent mess of ideas and objectives. The republicans have effectively hog tied themselves but they will win a lot of elections in the next few years.