Why can't we use magnetism for energy?

Magnetic shielding doesn't work that way. From the reference:

"It is important to remember that magnetic fields cannot simply be blocked. They can only be redirected away from the object or area you are attempting to shield. Magnetic shielding materials offer a very high permeability path for magnetic field lines, directing the electromagnetic energy through the thickness of the alloy, and keeping the field from going where it is not wanted. The shield must offer a complete path for the field lines, so that they do not exit the material in a place where they will cause unintended interference."

So the field would emerge from the ends of the shield, and would be ineffective. An effective shield would completely enclose the magnet-on-a-stick, but then it would be shielded from everything.

And all that's assuming we use bar magnets instead of the horseshoe magnets in the picture, which would simultaneously attract and repel, and so wouldn't work even if the shielding did.

We neither create nor destroy energy, it just changes form, that is the physical work in cranking a generator gets converted into electricity & some heat due to the friction in the bearings.

The concept of FREE energy has been around for a

LONG time and it really never works.

there isn't anything that is FREE, it gets accounted for somehow.

The magnets idea has been tried MANY times and found to simply not work.

The magnets would reach an equilibrium point and once there,

the machine would stop.

We humans here on this earth are using up resources at an alarming rate and

it amounts to living beyond our means. not a good idea.

We do use magnets every day to make energy. When you pass copper through a magnetic field it makes electricity. This is how most electricity in the world is made.

All electric motors use magnetism.