I agree that the parousia WILL be an invisible event. But one must think it through. If it happened at 70 A.D., or at any time before, then what would have been the consequences?
No matter what the date of the writing of Revelation, it is a historical fact that John was alive in the 90's and probably died in the second century. Was he left behind?
If all the believers were taken up during the parousia (rapture as I understand it), then Christianity would have died out right then and there. No one would have been left to carry it on. There would be no witnesses; no one to evangelize.
How do you account for these things.
There is no rapture as it is popularly conceived, so there is no physical separation, no group being physically left behind. The Kingdom was to come without observation.
And, yes, evangelism continues to this day. People are still coming into His kingdom every day.