The question of the alleged delay of Christ’s coming is complex, and a comprehensive discussion would be time consuming. I offer simply elements that should be taken into consideration in seeking to answer your concern.
1. A DELAY?
It is usually assumed by many that for some reason Jesus has delayed His return in glory. The general tendency has been to credit it to the spiritual condition of the church: we are still here because of our spiritual failure. The impression is then given that if we change that situation, the Lord will come.
But what if Christ has not delayed His coming? Do we have any evidence in the Bible showing that God has been postponing the Second Coming? That does not seem to be the case. This much we can affirm with full certainty: between the first and the second epiphanies of Christ, He is performing His high-priestly work in heaven, and the church is fulfilling its mission on earth.
2. THE MISSION OF THE CHURCH
Christ clearly told His disciples that the time between His two appearings was to be filled with the mission of the church (Acts 1:8; Matt. 24:45, 46). It was precisely in the context of attempting to find out when Christ would establish His kingdom that He pointed instead to the mission of the church, thus forbidding speculations on the topic (Acts 1:6, 7). He knew that debates about the timing of His coming would distract His people from fulfilling their mission, and would divide them and create conflicts among them. According to Jesus, those who say, “My master is staying away for a long time,” are the ones who create controversies and harm others (Matt. 24:48, 49). Therefore, Christ emphasized mission, not speculation and time-setting concerning His return.
3. PRIESTHOOD OF CHRIST
After His ascension, Jesus sat at the right hand of the Father and began His priestly work (Heb. 4:14; 8:1; Acts 2:32, 33). He is there interceding for us, making the atoning benefits of His substitutionary death available to repentant sinners (Heb. 7:25; 9:24; Rom. 8:34). At the beginning of His priestly work, Christ’s first request to the Father was to send to His people on earth the Holy Spirit that He had promised them, and that would enable them to fulfill their mission. The Father honored the Son’s request (Acts 1:8; 2:33). Christ would stay there until the time comes for the restoration of all things (Acts 3:21; 2:34, 35)—the consummation of His saving work (cf. Eph. 1:10). For now He is inaccessible to the natural human eye, but once He finishes His work in the heavenly temple, “He will appear [horao, passive, “to be seen”] a second time . . . to bring salvation to those who are waiting for him” (Heb. 9:28, NIV). The church waits for Him by fulfilling its mission.
4. THE SECRECY OF THE TIMING
The second coming of Jesus is part of God’s plan of salvation, formulated in eternity, and included the moment the first coming of Christ happened. God determined that toward the end of the 70 weeks the Messiah would come, whether people were ready or not (Dan. 9:24-27). God has always been in charge of times and seasons (Dan. 2:21; Acts 1:7). At some moment Christ will declare that the destiny of all humans has been determined and He will return, ending the mission and waiting of His church (Rev. 22:11) and the cosmic conflict.