You're wrong. Your failure to rightly divide the word of truth is the problem!The gospel of the kingdom was a very real gospel. The Lord Himself preached it (Matthew 4:23 KJV) and the requirements to be saved under that gospel to Israel past and future were/are:
Repent, and believe the gospel (Mark 1:4 KJV) by baptism of repentance for the remission of sins (Mark 1:4 KJV, Mark 16:16 KJV, Acts 2:38 KJV), keep the commandments (John 14:15 KJV, Matthew 23:2-3 KJV, John 15:5-10 KJV), endure to the end to be saved (Matthew 10:22 KJV), go through the trial of their faith (1 Peter 1:7 KJV), receiving the end of their faith, even the salvation of their souls (1 Peter 1:9 KJV). That salvation is of the grace that "should" come unto them (Acts 15:11 KJV, 1 Peter 1:10 KJV). They look forward that their sins may be blotted out, when the times of refreshing shall come from the presence of the Lord (which is at what many refer to as the second coming of the Lord (Acts 3:19-21 KJV).
That is not the same as:
the righteousness of God without the law by the faith of Jesus Christ that is unto all and upon all them that believe (Romans 3:21-22 KJV). To be saved today is to trust the Lord believing the gospel of Christ (1 Corinthians 15:1-4 KJV) which is where the righteousness of God is revealed (Romans 1:16-17 KJV). Those who have trusted the Lord today having believed the gospel of Christ "are saved" presently (1 Corinthians 1:18 KJV, 1 Corinthians 15:2 KJV,Ephesians 2:5 KJV, Ephesians 2:8 KJV). We are saved not by works of righteousness which we have done (Romans 4:4-5 KJV, Titus 3:4-7 KJV). We are baptized BY one Spirit into one Body (not by water for the remission of sins 1 Corinthians 12:13 KJV). We have now received the atonement (Romans 5:11 KJV).