1 MJ per second is 1 MW, a power level typical of portable diesel generators. Conventional nuclear plants are hundreds of megawatts each.
Apparently it is quite hard to repeat the laser blast quickly, because the optical system heats up during a pulse causing the beams to deflect as the materials expand and contract due to temperature. The NIF design requires dozens of laser beams to align precisely on a very small pellet in the middle of a large cavity. If you fire it a second time before it completely cools down the beams will hit the pellet slightly off-center and you won't get the compression needed for efficient fusion.
Apparently it is quite hard to repeat the laser blast quickly, because the optical system heats up during a pulse causing the beams to deflect as the materials expand and contract due to temperature. The NIF design requires dozens of laser beams to align precisely on a very small pellet in the middle of a large cavity. If you fire it a second time before it completely cools down the beams will hit the pellet slightly off-center and you won't get the compression needed for efficient fusion.