Firstly, the trinity only conflicts with a singular god if you understand them as being separate beings which only Gnostics and Gnostic derived sects argue to be the case.
Secondly it's worse than the pope merely being a representative, his titles claim that he is the replacement of Christ on earth..... making him an anti-Christ.
Then there is the cannibalism of the Eucharist, the history of literary frauds, the rewriting of the 10 Commandments, the killing of true believers, the totalitarianism, the worship of the dead, the worship of angels, the relic frauds, the purgatory racketeering, the homosexual cults protected by monasteries and nunneries, the altar boy problem, the devil popes, the Jesuit (Black Pope) problem, the banning of Bibles, the attempts to lawfully regulate all sexual conduct, the syncretism, the support of Nazi Germany in their attempt to eradicate Jews, etc
I find it very difficult from any perspective to find any kind of argument that they are actually Christians or that they even worship the real Mary and Jesus instead of Semiramis and Tammuz..... it's not even a "Christian" invention as the Israelite prophets had the same problem corruption popping up from the start.