The pro level stills are from houses with enough renderfarm power to chew up a scene quickly. A lot of the poor quality renders out there are due to incorrect settings or getting frustrated with how long borderline hardware is taking to render and dropping the quality of the worst offenders.....which is AA and lighting quality settings. And a lot of the flicker issues only show when animating, the vast majority are in the distance, where things are a lot more granular and virtual than close up is.