When it says that the Spirit is "removed", he isn't suggesting that the Spirit will be absent. Paul is talking about the Holy Spirit's role as "The Spirit of Truth." In his role, the Holy Spirit speaks for Christ and helps the Apostles convict the world of Sin, righteousness, and judgment.
John 16:7-11 This has a restraining force on the hearts of people and guides everyone in the light of Christ's teaching. We all live under the light of Christ's teaching, whether we are followers of Christ or not. As John said, Jesus is the light of the world.
But at a point in recent history, some would call it the postmodern era, truth is redefined as whatever we agree on by consensus. Modern philosophers don't even know if an objective truth actually exists. If we all agree that a man can have a baby then a man can have a baby. If we decide that a boy can play in women's sports, then they will be allowed. Whatever we all decide as a culture and society is "true".
We are living that delusion right now and since the world is not convinced that an objective truth is possible, then it is harder for the Holy Spirit to convict everyone of sin, righteousness and judgment. In my view, the man of lawlessness is right at the door. Satan has cleared his path.