Since the automatic adjusters are designed to work while stepping on the brakes in reverse, the effective braking isn't very good in that direction. Still, it should stop the car if pushed in hard. Only thing I can think of is if the shoes and/or drums are glazed over and not producing enough friction. Or perhaps the drums have been turned a bunch and the contact pattern on the shoes are very narrow? How does the contact pattern look on the shoes?
As a side note, which may or may not be of help, my cars braking had become somewhat lacking, which I only noticed when I started racing it and trying to slow down from 115 mph. My rotors had become glazed from 20+ years of use, but the pads still looked very good. I had my rotors turned to expose fresh meat on them, and still using the same old stock type pads, braking was massively improved. It went from making me nervous at the end of the 1/4 to having full confidence that I could stop without excessive effort. Of course that would not help if the contact pattern on your drums was minimal, but just passing it along as something to consider.