The 3 original seasons are a work of art in their own. Sure they are very different from the manga and their main story is probably less developped than the manga. But it created what is the series now, and it had an emotional and cultural impact that is yet to be seen from the manga (inner deathes in S1, Nephrite death, épisodes 110-111-124-125). Maybe the anime story misses some interesting points from the manga, I agree, but it’s still a vastly superior work, both graphically and from a storytelling point of view.