These things are not easy, simple fixes. Do you know how we know this? They weren’t done when the law was passed.
Why? Because Democrats couldn’t assemble a political coalition to do this. Mind you, at the time they had 60 votes in the Senate, and control of the House, and the presidency — a level of historical dominance they hadn’t managed in decades. Either these simple fixes would have pushed the price tag of the bill too high, making it difficult to find even more taxes or program cuts to pay for it, or they would have damaged the popularity of a bill that was already really unpopular.
And this is true of every idea that starts with “All we need to do.” If “All we need to do” to fix some substantial problem were cheap and politically popular, it would already have been done, and we wouldn’t be talking about it. The stuff we argue about is, almost by definition, the stuff that’s hard.
Needless to say, Republicans are not going to be eager to do something hard and unpopular largely in order to save a program that was passed over their strenuous objections and is now hurting their political opponents.