There were actually a few decent ideas that snuck into the bill (not that anyone would have known, as nobody read it). But the job certainly needs to be full repeal and then go back and try to pass to good elements by themselves. Selective repeal would just be a mess.
And letting so-called 27-year-old "children" use their parents' health insurance wasn't one of them. Letting able-bodied people in the prime of their life mooch off of others is one of the main reasons the welfare state is collapsing as fast as it is. And whether it's through state-run welfare or mandating the private sector provide welfare, it's the same thing. It lets these people survive while sitting at home doing nothing and not contributing to the tax base or the economy.