They aren't difficult to replicate because of deindustrialization, they're difficult and pointless to replicate because they were based around handcrafting, while modern rocket manufacturing is all computer controlled.
The designs are not optimal for modern production approaches.
As an example, a modernized F-1 engine would have far simplified plumbing, much fewer parts, the injector, which contained hundreds of handcrafted and hand-tuned parts to minimize combustion instability would be replaced with one machine crafted part where the instabilities would be properly cancelled out through computer simulation. But, what's the point?
The F-1s were designed because computer control systems of the time were not good enough to control a large number of smaller, more efficient engines. Nowadays such control systems exist, with Falcon Heavy flying 27 engines, and Starship doing 33. The fuel they used is also not really being seen as the future, with medium and heavy lifters shifting towards Methane for its better efficiency, cleaner combustion aiding reuse and being liquid at similar temperatures to oxygen, simplifying the cryo-tank design.
They simply aren't relevant anymore outside of out of touch Congress critters looking for ways to pour more billions into the dead end of SLS.
The other big point is that Saturn V wouldn't even meet the expectations current lunar landers are expected to meet. Both lander proposals are huge, potentially with the habitable volume of the entire ISS. They could, on their own, serve as small long term lunar bases, if it weren't for Orion being unable to spend an extended time in space.
The designs are not optimal for modern production approaches.
As an example, a modernized F-1 engine would have far simplified plumbing, much fewer parts, the injector, which contained hundreds of handcrafted and hand-tuned parts to minimize combustion instability would be replaced with one machine crafted part where the instabilities would be properly cancelled out through computer simulation. But, what's the point?
The F-1s were designed because computer control systems of the time were not good enough to control a large number of smaller, more efficient engines. Nowadays such control systems exist, with Falcon Heavy flying 27 engines, and Starship doing 33. The fuel they used is also not really being seen as the future, with medium and heavy lifters shifting towards Methane for its better efficiency, cleaner combustion aiding reuse and being liquid at similar temperatures to oxygen, simplifying the cryo-tank design.
They simply aren't relevant anymore outside of out of touch Congress critters looking for ways to pour more billions into the dead end of SLS.
The other big point is that Saturn V wouldn't even meet the expectations current lunar landers are expected to meet. Both lander proposals are huge, potentially with the habitable volume of the entire ISS. They could, on their own, serve as small long term lunar bases, if it weren't for Orion being unable to spend an extended time in space.