Saying Our Fathers and Hail Mary’s is hardly penance either yet that is the typical penance for even mortal sins.
Maybe if people had to scrub the bathroom floors on their knees, or mow the lawn with a hand mower, or cut up firewood with an ax, as penance, they would think twice about sinning again. More likely though they would think twice about going to confession...:)
Regardless of all that, I am in favor of going back to meatless friday’s because even though it is not much of a sacrifice you still have to think about it and about why you are doing it. It is the thought that really counts.