flavorless
Having no taste and seeming plain or boring.
Flavorless means having no taste or such a weak taste that you barely notice it. When food is flavorless, eating it feels like chewing on nothing: a flavorless soup might as well be hot water, and flavorless chicken tastes more like nothing than like real meat.
The word also describes things that lack energy, personality, or anything distinctive. A flavorless performance in a school play would be one where the actor says all the right lines but brings no energy or personality to the character. A flavorless story might have all the basic parts (beginning, middle, and end) but feel boring and forgettable because nothing interesting really happens.
Think of flavor as the special quality that makes something worth experiencing. When we talk about gelato having intense flavor, or a musician having a flavorful style, we mean they have something distinctive and memorable about them. Flavorless is the opposite: it's when something is so plain or ordinary that it leaves no impression at all. Even foods that are supposed to be mild, like plain rice or tofu, have some subtle taste to them. Something truly flavorless would taste like nothing at all.