One of the biggest mistakes in dining lighting is getting the scale wrong. A fixture that is too small can feel like an afterthought, like it was picked to fill a requirement instead of actually support the room. Go too big, though, and it can overwhelm the table and pull attention away from everything else. Dining rooms usually feel best when the fixture has presence without turning into the whole story.
Hanging height is another common problem. If the fixture is too high, it loses connection with the table and starts to feel disconnected. Too low, and it can become distracting or awkward. There is a middle ground where the light feels tied to the table but still leaves the room open, and that is usually where things click.
Brightness gets mishandled a lot too. Harsh light can make the room feel flat and uncomfortable, while weak lighting can leave everything looking dull. A dimmer solves a lot of that, but people skip it all the time. Same goes for placement. If the fixture is not centered properly over the table, the whole room can feel slightly off, even when nothing else is obviously wrong.
Most dining lighting mistakes are not huge on their own. They just add up fast.