The God of the Covenant versus the God of Dispensationalism

The doctrine taught by dispensationalists (that is, classical dispensationalists, such as Scofield) that I find most objectionable is that God has provided different methods of salvation down through history, as man has failed each previous one. Some of them claim, for example, that Jews were (or still are, some say) saved by obeying the Law. They claim that salvation by grace through faith only became an option when the Jews rejected their Mosaic Messiah by killing Jesus. Grace through faith is Plan B. Actually it is Plan G, if you go by Scofield's seven dispensations.

I think that is ridiculous! And, apparently, so do most dispensationalists, because few still hold to that doctrine. Yet, even these progressive dispensationalists, as they call themselves, place a firewall between the Old Testament and the New Testament. In order still to be applicable, they claim, an Old Testament commandment must be repeated in the New Testament.

Where is the biblical justification for that claim? I can't seem to find it.

Rather, I find just the opposite.

One problem with that is that it has God coming up with a new plan, because His previous ones have failed. What kind of God is that?

In contrast, the bible tells us of God that, "God is not man, that He should lie, or a son of man, that He should change His mind. Has He said, and will He not do it? Or has He spoken, and will He not fulfill it?" (Numbers 23:19). And, "The Glory of Israel will not lie or have regret, for He is not a man, that He should have regret" (I Samuel 15:29). In other words, the God of the Bible is not a bumbling human being, who cannot achieve what He says, and has to come up with contingency plans! Yet, that is exactly the God described by dispensationalism.

In contrast, the God described by covenant theology is a God who has had one plan from before the creation of the world. He has had one expectation, that man would fall into sin; it was not a surprise. And He has had one plan to deal with sin, to send His divine Son to shed His own blood for those sinners chosen for salvation. That plan was first revealed, in seed form, in Genesis 3:15, called the Protevangelium by theologians: "I will put enmity between you and the woman, and between your offspring and her offspring; He shall bruise your head, and you shall bruise His heel." And that plan has been shown in increasing light ever since, until it was achieved on the cross and in the resurrection of that same Son, Jesus Christ. More light, not different light.