Ah, but you Latins went soft and started allowing fish and dairy products on fast days. In the East fish is what we put back on the menu to whoop it up when a major feast day falls in a major fast or a Wednesday or Friday, as Annunciation and Palm Sunday always do. (And to think back in the day when we were all in communion you used to be more strict — no katalysis on Saturdays.)
The medieval Catholic church had so many meat-free days. Something like 180! That’s why no archeologist or scientist was surprised when they found that King Richard III mostly ate fish!