Zoom lenses vary considerably in design and optical quality. As you would expect, precision systems are correspondingly more expensive, and are generally much larger.
Whether any lens’s limitations are apparent, will largely depend on the kind of subjects you are shooting. Where your audience is concentrating on the action (e.g. newscasts), or the subjects themselves are less critical (e.g. general location shots), any shortcomings will usually be overlooked anyway. But there are situations where any defects will be obvious to even the casual viewer.
If for instance, you take close shots of graph paper, sheet music, maps or fine print, and slowly zoom in and out, you may well find that:
• The image is not as sharp ...