I think it bears mentioning that at the moment the pendulum is somewhat on the side of congressional over-spending. There has been the ongoing issue of congress forcing the pentagon to buy more Abrams tanks to spite their strategic irrelevance (we have more than enough to satisfy our needs) because they want to keep the manufacturing lines running.
Now we're in a society of permanent volunteer military readiness, and we have to deal with endemic problems. The corruption and solutions both look different, and solutions have to have sustainability in mind.
I think you might be right, that Congress right now does spur on overspending rather than underspending. It's just about impossible to close a base anywhere, from what I hear. Still, in the long run, I do think it's better that Congress keep control of this and have continual oversight. I think it might be better suited to the Senate, and I think it's better suited to committees, but there does need to be a accountability there that is entirely outside of the military.
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