I just noticed he quoted and viewed many books which are not scripture now as scripture. Is this why he is not venerated in the Catholic Church anymore?
In Clement’s 2nd Century AD, there was no well defined Canon of Scripture, so that was not the reason. His views were sometimes unorthodox. Read the Catholic Encyclopedia article on Clement for some discussion:
When the Roman Martyrology was revised by Pope Clement VIII, Clement of Alexandria’s name was dropped from the calendar on the advice of Cardinal Baronius. Benedict XIV maintained this decision of his predecessor on the grounds that Clement’s life was little known, that he had never obtained public cultus in the Church, and that some of his doctrines were, if not erroneous, at least suspect.