As mentioned in post #15, the passages you cited describe natural marriages between Jews- not sacramental marriages of Christians. The Church has always taught that Jesus raised marriage back to the level of a sacrament. See Mark Chapter 10
I’m not Catholic; I don’t believe that ‘church teaching’ is authoritative, only Scripture.
But to answer your objection, if Jesus was changing the institution of marriage, why did he say ‘From the BEGINNING it was not so’? Look at the original text in Greek, and you get that marriage is marriage no matter when it happens; there was never any change in God’s intentions for marriage when he gave the Law to Moses.
God made allowances for divorce because he knows that sin happens, and he did so in order to protect the wronged party. In the Christian life, we also must take marriage VERY seriously.
But if divorce DOES happen, and it will, and if remarriage does happen, and it will, then we can look at the other examples in Scripture to know what to do about it.
God says very clearly that remarrying your original partner after divorcing a second wife or husband is abominable. I see no reason to argue with that.