I think it was two things, focusing too much on gimmicks and quality of opponents. His best WCW bouts were with Guys like Austin and Windham. Although he doesn't get credit before his neck and knee issues, Austin could go.
Also I guess the character called for him to move about the ring in quite a robortic fashion and that didn't help. Defently who he faced was a big factor, his match with Ultimate Warrior has to be one of the worse matches I have ever seen. His best match of the early Goldust years was the Back Lott Brawl against Piper really like that match.
Troy I was a big fan of the early character as it was far more edgy and unpredicatable, and the refenences to movies was a nice touch. Post-1997 it really got watered down, although I did enjoy the run he had later with Booker T.