While Truman was still a Senator, he was head of what's today known as the 'Truman Committee'[0]. During WWII, there were tons of instances of budget bloat and shoddy manufacturing that were both too expensive to taxpayers and put Americans' lives in danger overseas. This saved tens of millions of 1940s dollars, and gained Truman the widespread political appeal that helped him eventually win his Vice Presidency.
I think a general point is, the military needs oversight, and we are a democratic country. For now, it might seem reasonable to you that Congress might not make the best decisions about military readiness, but removing the ability from Congress to decide that they should have the ability to investigate and shrink military budgets is un-democratic. I can easily imagine a world where we remove line-item oversight from Congress, and in 50 years, military spend is like it was multiple times in the history of other empires: not up to date, bloated, profitable to those in bureaucratic control, and an unpleasant surprise when we need it most.
I think you're totally right, the carriers are still important, particularly if we're not in a hot war. Carriers are second-to-none for establishing land/air/sea superiority. But if the military believes that, it should make that case to Congress, and Congress should do what they do with a recognition that they are beholden to the American public for their decisions.
[0] https://en.wikipedia.org/wiki/Truman_Committee