Not quite, stanley.
Since Fridays are held in Christian tradition as remembrance days of Jesus’s dying on the cross (on GOOD Friday), pious remembrance practices of doing PENANCE arose, from the earliest Christians onward.
During much of history on the European continent and the British Isles, until the 19th and 20th centuries, MEAT was a LUXURY item. Most people were lucky if they ate wheat bread, oat bread, root vegetables, and fruits in season. If they lived near water, they fished. MEAT was rare. So, since it was a LUXURY, it was considered a penance to go “without it” on a day of penance.
If you say that “Catholics used to think eating meat on Friday was sinful”, what do you say about the Methodists and the Mormons? What do you say about Jews who keep kosher? What do you say of Muslims who fast during Ramadan? All those people refrain from perfectly normal activities (eating food) for a REASON. . .it is not the EATING which is sinful, but the eating at a particular time when one CHOOSES to exercise penance. . .to offer up to God a sacrifice, in choosing NOT to eat a food which one likes, or choosing not to eat during the day (Muslims) or choosing to eat certain foods which one feels God allows, and not to eat others He does not (Jews).
But, stanley, meat, though still $$, is not a luxury. And lots of people are vegatarians, or trying to limit meat consumption. In order to make people actually THINK about penance and (in the case of those who already didn’t eat meat anyway) give them an opportunity to do a real penance, we lucky Catholics may observe penance and sacrifice and give honor and glory to God in many ways. Some of us may still choose to have a meatless Friday (those who really like meat DO sacrifice in not having it), and others may choose to say extra prayers, to go to Friday Eucharistic Adoration, to work in a soup kitchen, or to give up other favored foods, or activities.
It is not the food or the activity that is sinful, if indulged in, but the DISOBEDIENCE behind the indulging in.
So stanley, if you don’t want to do a penance, if you don’t believe you have to, you aren’t sinning.
But if you have tradition dating back 2000 years, a love and respect for God, an understanding of what sacrifice and penance means, and a wish to serve, to give up something freely as a way to thank God for HIS gifts and as a small token of our love, as a child might take a cookie given to him by his father and seek to give it to the father in return–a loving gesture which is certainly appreciated by the father even if he does not need the cookie–then you MIGHT be able to grasp what “Friday penance” should mean to Catholics. I wish you luck. God bless.