You are not getting the fact that Paul was writing to the Church about two separate events.
I do get that, but I see it differently from how you are reading it.
2Th 2:1 Now we beseech you, brethren, by the coming of our Lord Jesus Christ, and by our gathering together unto him.
The coming of the Lord Jesus Christ is about Jesus's second coming to the earth to destroy the Antichrist. Then he tells them that day (His second coming, not rapture) will NOT happen until there is a falling away first, and the man of sin be revealed. Someone convinced them they had missed the rapture, and they were about to go through the tribulation.
On the contrary, since you acknowledge that he is talking about 2 events, then the falling away from the faith is to happen first for which the Lord by His appearing as the Bridegroom will deal with and THEN the other event which will happen after the rapture & midway in the great tribulation of that man of sin being revealed.
The second thing Paul told them was about the "our gathering together unto him" referring to the Church being raptured, NOT Jesus's second coming.
The rapture will happen before the revealing of the Antichrist, which is by the removing of the "restrainer" who is the Church so that the man of sin can be revealed.
The man of sin will be revealed when he enters the Holy of Holies in the third Temple and declares himself to be "god". The Church has nothing to do with keeping the devil in his place or hidden.
Look at 2 Thessalonians 2:13-15 and see that traditions taught of us as to when we had received the promise of the Spirit was at the calling of the gospel when we had first believed in Him. That was the line of discernment to see the iniquity that was already at work in Paul's day in misleading believers away from the faith in Jesus Christ in believing the lie that they can receive the Holy Spirit again apart from salvation... and again and again and again after signs of confusion.
That was in reproof of those falling away from the faith mentioned in the previous verses as being damned because they love not the truth that we had received the promise of the Spirit by faith in Jesus Christ at the calling of the gospel whereby they have gone astray in giving heed to seducing spirits and doctrines of devils; if you know about "slain in the spirit" , "holy laughter movement" , Pensacola Outpouring, Toronto's Blessing, Ernest Angeley's Healing Crusade, and even the baptism of the Holy Ghost with evidence of tongues, then that is the falling away from the faith Paul was talking about where saved believer believed the lie that they can receive the Holy spirit apart from salvation. See? That is happening now.
There have been millions of people in the Church that have, and are still falling away from the faith. Read the parable of the sower, and you will find out why that happens. The falling away are those who have never been saved yet they are apart of the Church, but only in flesh, not in spirit.
The ones that the seeds were gobbled up are the unbelievers that did not receive the seed of Christ to be saved. All others are describing how not every saved believer will bear fruit as His disciple, but the one that does are His disciples. Only the chosen that are His disciples as found abiding in Him will be received as vessels unto honor in His House at the Marriage Supper when the Bridegroom comes.
2Th 2:10 And with all deceivableness of unrighteousness in them that perish; because they received not the love of the truth, that they might be saved.
These are the "falling away" ones. They were never saved at any time yet they were in the Church!! Because they never received the salvation of the truth that they could be saved, so God gave them a strong delusion to believe a lie.
2Th 2:11 And for this cause God shall send them strong delusion, that they should believe a lie:
A person is either in Christ or Not in Christ.
A saved believer can be found not abiding in Christ as even former believers are to be called to depart from iniquity so they can be received as vessels unto honor in His House; see 2 Timothy 2:18-21 . If they purge themselves of iniquity, they are what? Vessels unto honor. If they do not depart from iniquity, they are what? Vessels unto dishonor. Where are the vessels unto dishonor? Still in His House. If you look at the prodigal son in how he gave up his first inheritance ( vessel unto honor & crowns ) for wild living, he can never get it back, but he is still son. That is the power of God in salvation for all those who believe in Him, even in His name ( John 1:12-13 ) That is why they are still in His House.
Each believer will be judged by what they have placed on that foundation which was laid by Christ Jesus. ( 1 Corinthians 3:10-17 ) In that day ( 1 Corinthians 3:13 ) which is the pre great trib rapture event when God judges His House ( 1 Peter 4:17-19 KJV ), believers will be judged by their works on that foundation and if there be any work of iniquity still on that foundation when the Bridegroom comes, they shall be left behind as castaways to be "damned" as vessels unto dishonor in His House for not looking to Him for help in discerning as well as departing from iniquity.
So the call to depart from iniquity by looking to the author & finisher of our faith to help us lay aside every weight & sin is how a saved believer is to love by faith in Jesus Christ as our Good Shepherd in helping us to follow Him as His disciples. That call is to be given even to former believers because He still resides in them ( 2 Timothy 2:13 ) Hopefully, the Lord will help you to understand why I believe what I do, even if you still disagree with it, but I can hope in Him to cause the increase for you to agree with the actual meaning of His words to be on this issue.