1992 Mazda 323 low brake pedal

The pedal bottoms out, so there is no reserve pressure. In most cars, I can push the pedal and feel pressure after the brakes are locked, but not this one. It feels like the brakes fade. The emergency brake seems to stop the car faster than the main brakes. If the car sits for a few days, the right rear wheel will skid the first few times the brakes are used, but if I jack up the rear wheel, it spins freely, so that brake is not dragging. Parking brake works. After repairing leaky brake lines, replacing both rear wheel cylinders, replacing the master cylinder, and bleeding all the lines, I still have this problem. There are no leaks now. Rear shoes are possibly over half worn, but not worn out. Is it possible my adjusters are not working or drums are oversized, so the shoe travel distance is too great? What else could cause this symptom?