It really depends on what you mean by bad? But like Quartz, during that time there wasn't a very evolved style such as the Black & White spriting style where the shading is very simple and there are dark outline. During Quartz, the style was very much like the Ruby, Sapphire and Emerald style where there would be more colours and a much more complex shading than it is currently and many, many highlights.
I guess the reason we call Quartz sprites bad nowadays because we have a new style and most of us believe that the new Black & White sprites are the epitome of Pokemon sprites. We pay too much attention to the new sprites and we end up comparing all of the new fakedex's and new fakemon to the current official style. But I think the concept is very important as well when it comes to judging a sprite because I remember seeing Babos from Pokemon Quartz and that thing was... unusual.