The Deadly Sin of Gluttony does not consist in eating a lot. It consists in consuming more than you can afford. In harsher times, that did mean Death indeed — yet an indirect Death that had to be warned about for it wasn't obvious to the naive and the ignorant. In modern times, consuming more than you can afford still means Death, but in a yet more indirect way, that requires oh so bigger warning. There are enough interpersonal safety nets and economic interconnections that Gluttony is not usually deadly at a personal level — but it remains Deadly, and how Deadly, at a societal level. Gluttony is socialism and everything left wing: denial of scarcity, spending as if from an infinite barrel, "unblocking" the manna from above. But the manna isn't from above, it's the blood and sweat from the producers being oppressed, and the more they are oppressed the less they produce, until the very richest country in a continent (Rhodesia, Venezuela) becomes the very poorest, and people starve and die.
The big mistake that modern people make with respect to their ancient predecessors is not disagreeing with them — it's failing to understand them. Our ancestors weren't more stupid, naive or credulous than we are. Their disadvantage compared to us is that they lacked the accumulated product of thousands of years of riches, of wisdom, of experience, of technology, of social skills — in a word, of capital — whether material or human.