No, I do not believe that is correct. The key thing to understand here is the difference between torque and power. A sustained climbing effort will not be difficult because a rider struggles to generate sufficient torque but, rather, because they struggle to generate sufficient power.

For the same pedal force and cadence, increasing the crank length will increase the leverage and the power output. However, that additional power still has to be supplied by you. The force that you apply to the pedal now has to travel around the circumference of a larger diameter circle. And that increases the input energy demand per revolution. So, all other things being equal, it will be more difficult to climb with longer cranks unless you reduce your cadence commensurately (in which case, by definition, all things are not equal).

There's just no free lunch in Newtonian physics.

The same principle works in reverse for short cranks. A pedal stroke is akin to a one legged, partial squat. All else held constant, a shorter crank will make the squat more partial and allow the rider to generate more pedal force (just as with a real, partial squat). However, because that force will now travel the circumference of a smaller circle, the net effect on power is no effect at all.

This linear trade-off is valid for the bike because bikes are very simple machines. A human body, on the other hand, is a vastly more complex machine. Muscle contractions are more efficient at different speeds, fatigue can spread out when more muscle motor units are recruited, etc. As a result, optimal pedaling efficiency is about dialing in the efficiency sweet spot of the body and not the bike.

I realize that you asked for a simple explanation sans equations. Unfortunately, this stuff cannot be grasped meaningfully without at least this much physics.