My definition of bland food may differ to yours, but to me it’s usually boiled or maybe roasted or fried without much in the way of seasoning – what some might call “simple fare”? For example even if a boiled chicken may be flavoursome, without seasoning it would still be defined as “bland”? Thus in my opinion bland food can still be as good as well seasoned food.
To me unappealing food is dull lifeless, overcooked, (frozen) vegetables, dried out overcooked (frozen) meat/fish. The blandness is not so much of a factor, the quality of the ingredients and mode of preparation is. My point is that the blandness can be overcome if the quality of the ingredients is there, if it’s not then more seasoning is needed… but that still cannot turn bad produce into good produce, it merely masks it somewhat. As to your question, some people cannot deal with strong flavours and spices, because they’re simply not used to them. A lot of eating is an acquired taste. I pretty much eat everything so I don’t fully understand why certain people refuse to eat certain things, often based on a certain bad experience years in the past.