It is not Biblical to say that God is saving people who reject Christ, and this is not what dispensationalism teaches.
It is also not Biblical to say that God completely replaced natural Israel, when in fact we are clearly told "All of [natural] Israel shall be saved" in the future in Romans 11:25-26.
We clearly see in Zechariah 12 that natural Israel will be surrounded and under attack from "all the nations" (Zech 12:2-3) and Israel prays and is sent the One "whom they pierced" (Zech12:10-11). So you see Israel gets saved by crying out humbly to YH and then Christ comes to save them. This lines up precisely with what Jesus said in Matt 23:39 when He said to the Pharisees and specifically Jerusalem they would "see Me no more till you say, "Blessed is He who comes in the name of the Lord!". (Matt 23:37-39)
God will bring back natural Israel in the latter years (Ezek 37:12, 38:8, Lk 21:24, etc etc) and Honor the covenant He made with natural Israel in Genesis 15. How do we know this? Well two very clear reasons we can conclude this are:
1. God has spoken many unfulfilled prophecies pertaining to natural geographic Israel and surrounding nations that have yet to be fulfilled- and we are seeing them being fulfilled. (Dan 9:24-27, Ezek 37-39, Dan 11:35-12:4, Joel 3, Ps 83, Zech 12-14)
2. Paul very explicitly said that "Israel has been blinded in part until the period of the Gentiles is fulfilled. And so, as it is written, ALL OF ISRAEL SHALL BE SAVED" -Romans 11:25-26.
Spiritually Jews and Gentiles are one in Christ, yet God still made a covenant with natural Israel in Gen 15 which He will honor. Men and women are one, and have different purposes and positions. Members of the Body of Christ are one, and still have different functions and purposes. This is not a contradiction.
If replacement theology was true, then why is God literally fulfilling all the prophecies in the Word systematically in front of our eyes?!
Dispensationalism is a false doctrine of men that tramples on the Word of God