Regardless of their reasons for changing it, Kazemon, the facts still stand. The quality of the animation dropped severely, and was inconsistant, the original plot for the story was displaced, the personality of the characters changed, and the very atmosphere of the series were altered from what CLAMP had intended it to be, as a result of many smaller modifications. Pairing preferences or KuroFai-ness aside, they changed the series, and to those who have never read the manga, ruined the original story CLAMP created, by these changes.
As far as creating an anime based off of a manga, they failed massively. Simple as that.