But if this process like most things has diminishing returns, then wouldn't after a while government use up all the "easy wins", leaving only things to do that

But if this process like most things has diminishing returns, then wouldn't after a while government use up all the "easy wins", leaving only things to do that have a mix of good benefits and bad side effects. And once the best of these things were done, the remaining options would be more and more "bad side effects" and less and less "good benefits".