The Hebrew prophets discussed a coming Messiah and Isaiah gave enough detail to confirm a new covenant as well. So Christianity coming out of Judaism isn't a surprise. Now, Jews may not agree that Christianity IS that covenant, but the existence of Christianity doesn't surprise Jews. Make sense? However, in the Jewish prophets' writings we see that after this Messiah and his kingdom there will be no other and in the Christian New Testament (Covenant) writings we see the clear statements that this is the end of divine revelation.
So...Islam and Baha'i only make sense if they are the fulfilment of Old Testament prophecies rather than Christianity. It wouldn't make sense to build them as an addition to Christianity. When this is done it is fairly easy to refute by those knowledgeable in the writings. However, as we all know, if a person is committed to a way of thinking it's probably a done deal.
Basically I agree with you but I take issue with some points. Christ is the fulfilment of prophesies in every book of what we call the OT; in Minor Prophets a new covenant is promised but the timing of it is given in Daniel. Christianity is not that new covenant; Most Christians have abrogated the covenant or nailed it to the cross; in this sense most Christians are not different to other religions.
The 4 Gospels are the history of Christ making the new covenant; who He is making it with – the Jews and the lost sheep but not the gentiles; the apostles, the other disciples and Jesus are the new priesthood; Jesus is the Lamb of God from the foundation and the blood shed for the remission of sin; but in the middle of His 3 1/2 of making the new covenant before He is cut off, is the sermon on the mount He declares, Matthew 5:17-18 (KJV)
17 Think not that I am come to destroy the law, or the prophets: I am not come to destroy, but to fulfil.
18 For verily I say unto you, Till heaven and earth pass, one jot or one tittle shall in no wise pass from the law, till all be fulfilled.
The Law and the prophets are the covenant and won’t be changed till heaven and earth pass, till all is fulfilled. To my mind this covers eternity; it certainly covers the fulfilment of Revelation.
The Law /covenant goes to the Gentiles at and after Pentecost and after chapter 3 in Acts.
““However, as we all know, if a person is committed to a way of thinking it's probably a done deal.
Many people might have attained wisdom had they not assumed they had it.””
People may think the scriptures say differently but that matter was determined at the council of Trent when the Catholic challenged the Protestants, “If you go by the Bible and the Bible alone you will have to keep the fourth commandment, including Saturday, because there is no other authority for keeping Sunday or for not keeping the Law other than the Papacy”, and this stopped the protestants dead in their tracks. This getting off topic, I am preparing to start a thread on the New Covenant.