It's official canon that a lightsaber is a short beam of very powerful destructive force, like a chainsaw or a blowtorch. Only Jedi (or Sith) can use them because you need the skills of a Jedi not to injure yourself or someone else with such a powerful weapon.
But what if it's the opposite?
It actually makes more sense to me if the blade of a lightsaber is an extraordinarily weak, but extremely precise force. The Jedi are so attuned to the Force that they can find the spaces between individual atoms and sever the bonds holding a wall or an arm together. Similarly, they can find the force of another lightsaber and block its passage. But a non-Jedi like me or Admiral Ackbar would find it easier to injure someone with a laser pointer.
This idea is based on the Taoist text
Cutting Up an Ox in which a butcher explains that his skill at ox-dividing is due to the Way. He sees the "spaces in the joints" and makes so little effort that his blade is still sharp after 19 years of use.