I agree with your core point, but a blockade would not work to destroy most habitable planets. Most habitable planets in Star Wars are at least capable of self sufficiency. You would hurt their economy certainly, but most could produce enough food and other necessities to maintain a (possibly diminished) society.

Coruscant is likely an exception. That one has been turned almost entirely into one city and has virtually no farmland, certainly not enough to support even a fraction of its population.