This is a really big point actually. When I'm growing salad greens, you have to stop giving them nutrients about a week before harvest, so the plant can burn through those saved up nutrients, otherwise it straight up tastes like metal/vitamins.

Does any lettuce taste good? It all tastes like wet grass to me. At least spinach has flavor.

If it tastes like lettuce, just throw any combination of oil, salt and bit of sweet and you're good to go