1. That eventually someone will come up with a way of detecting it... rendering all of these crazy expensive stealth a huge waste of taxpayer dollars.
2. That if stealth can be used on boats, bombers, and fighters.. it can be used on nuclear armed ICBM’s too... which completely eliminates the ability to retaliate in a nuclear war since you are destroyed before you ever know your under attack.
The stealth here is mostly in the angles that the ship is built with that reflect the radar up and away.
They might also try to use some of the radar absorbing coatings but I have my doubts that that will stand up well to a marine environment.
ICBMs are mostly detected by their heat signature in the boost phase not by radar. It'll be a while before that can be hidden but a really large rail gun hidden in a mountain might just do the trick.
I'm not sure why this is so expensive. All most all of this technology has already been developed and paid for.
Maybe not a long while. An air-launched hypersonic missile would not have the heat signature of a silo launch.
"Our two biggest problems are gravity and paperwork. We can lick gravity, but sometimes the paperwork is overwhelming." - Werner von Braun
Navy warships have been using RAM (radar absorbent material) in the form of tiles and blankets for quite some time and, like everything else in a marine environment, require attention and maintenance.