:bigyikes: it supposedly goes all the way back to St Peter now? Back in my day it was just one of the medieval Popes who had relatives in the fishing industry who was supposed to have begun it…
Very simply, abstaining from meat does not mean, and has never ever meant, that even a single person has ever been obliged to eat fish
In fact many of the older and/or stricter fasts which have been adopted from time to time forbade things like fish and even eggs as well.
Put it this way. Fasting as a general principle, in some sense of the word, is a requirement of our faith, just like having ordained priests, or the celebration of Mass, is too.
What form that fasting takes (whether it includes eggs, fish, dairy, chicken or capybara) is a discipline, like whether Mass is all-Latin TLM or all-vernacular NO or one of the Eastern Divine Liturgies, or whether clergy can be married or not. And currently the discipline is the meat of warm-blooded land animals.