Quran is here because of the fact that people amended the holy books, which came prior to Quran.
currently, Christianity, and Judaism are not present in their original form. We have even amended Islam in every possible shape that is why these days we see so many sects of Islam. However, for Quran ALLAH SWT has taken the responsibility in HIS hand, so no human can change it.
and i dont know how much you have studied monotheistic religions but the current imagery of Christianity, and Judaism are something that was considered pagan imagery at the time they were built. Since these imageries have survived centuries, so they have gained the status of holiness.
the Ayat I have posted has simple meaning, only to marry Believers of the Oneness of ALLAH SWT. whereas Trinity or following peer-fakeers is opposite to what ayat is asking for.