The ascension of Jesus Christ is a central doctrine in the Angelic Conflict. Without it, there would be no positional truth for believers. Acts 1:7-11.
“He said to them, “It is not for you to know times or epochs which the Father has fixed by His own authority; but you will receive power when the Holy Spirit has come upon you; and you shall be My witnesses both in Jerusalem, and in all Judea and Samaria, and even to the remotest part of the earth.” And after He had said these things, He was lifted up while they were looking on, and a cloud received Him out of their sight. And as they were gazing intently into the sky while He was going, behold, two men in white clothing stood beside them. They also said, “Men of Galilee, why do you stand looking into the sky? This Jesus, who has been taken up from you into heaven, will come in just the same way as you have watched Him go into heaven.”“ (Acts 1:7-11, NASB)
There was no indwelling ministry of the Holy Spirit for believers until the ascension of Jesus Christ. Acts 1:1-2; 1 Cor. 12:13.
“The first account I composed, Theophilus, about all that Jesus began to do and teach, until the day when He was taken up to heaven, after He had by the Holy Spirit given orders to the apostles whom He had chosen.” (Acts 1:1-2, NASB)
“For by one Spirit we were all baptized into one body, whether Jews or Greeks, whether slaves or free, and we were all made to drink of one Spirit.” (1 Corinthians 12:13, NASB)
There was no priesthood among believers without the ascended High-Priest. This is the whole context of the book of Hebrews. Heb. 1:3; Heb. 1:13.
“And He is the radiance of His glory and the exact representation of His nature, and upholds all things by the word of His power. When He had made purification of sins, He sat down at the right hand of the Majesty on high,” (Hebrews 1:3, NASB)
“But to which of the angels has He ever said, “SIT AT MY RIGHT HAND, UNTIL I MAKE YOUR ENEMIES A FOOTSTOOL FOR YOUR FEET”?” (Hebrews 1:13, NASB)
It is impossible to have a mediator without the ascension. God the Father accepted the resurrected humanity of Jesus Christ and we accept Jesus Christ as our Mediator and Savior. 1 Tim. 2:5; Job 9.
“For there is one God, and one mediator also between God and men, the man Christ Jesus,” (1 Timothy 2:5, NASB)
Jesus Christ would not be our advocate without the ascension, nor could He intercede for us. 1 John 2:1-2.
“My little children, I am writing these things to you so that you may not sin. And if anyone sins, we have an Advocate with the Father, Jesus Christ the righteous; and He Himself is the propitiation for our sins; and not for ours only, but also for those of the whole world.” (1 John 2:1-2, NASB)
There would be no Church, no Rapture, and no Second Advent without the ascension. The ascension is a central doctrine in the whole plan of God.