You lose HP and die if the enemy hits you with an attack that reduces you to 0 or less, and then you fail three Death saves. HP are absolutely important, and trying to eat food to heal when you are lying unconscious and dying is not going to work. Nor is eating food that restores 1-6 hp likely to be a good strategy when the enemy are hitting you for 2-12.
Have you actually played the D&D game before, because I am curious as to how anyone would declare that HP and levelling up were not important.
