When you replaced the brake shoes did you FIRST UNHOOK CABLES FROM BACKING PLATES and THEN back off the brake adjuster near the top of backing plate under a rubber cover. After replacing shoes did you adjust FIRST the brake shoes against drums and THEN adjust the cables to be just free from pulling brake shoes out.
It will take some time for shoes to wear in and give full brake action, unless you have had the drums trued before replacing shoes.
Remember that these are NOT HYDRAULICS and dont work anywhere near as well? Its like the early pre 1930s autos that had cable or rod controled brakes. GOOD OLD DRAG YOUR FEET TYPE BRAKES.