the drums/pads need to be broken in or burnished. theres different procedures for this but most are basically doing some medium pedal force stops from about 35-40mph down to 5mph, not stopped. repeat at least 10 times with a minute or so cool down between. then do a few more at more aggressive braking from a little faster speed. you can google brake pad/shoe break in procedure for tips from many places, or call the brake shoe companies tech line to ask what they recommend.
take it out on a back road with minimal traffic & do a few of the slow downs and you should feel the brakes improve. heres just one link from summit, its for pads but the same process is done for shoes, you want to get a layer of brake shoe material on the drums. also want to turn used drums if they are within spec or if no signs of warping at least hit them with some 80 grit sand paper in a criss cross pattern.
https://help.summitracing.com/app/an...-and-rotors%3F