To fit the futurist theory, you have to ignore the very first verse of the book, which states that it concerns "things which must soon happen". An angel told Daniel to "seal up the book" because they described things which would happen 500 years after he wrote. An angel tells John that he's writing about events which "must soon happen," and they're 2000+ years in the future? Doesn't make sense.
There is no other world-historical event in the Christian era, after the resurrection and short of the Second Coming, which can compare to the fall of Jerusalem in AD 70. In one fell swoop, God put an end to the sacrificial system of the Mosaic Law, because the New Sacrifice had arrived and been instituted, the one that could actually take away sins, as Hebrews notes the blood of bulls and goats could never do.
It makes no sense that the NT would not take note of these events. I believe it did, but didn't record them as history in retrospective, but as prophetic utterance. And it recorded them in two books, Hebrews and Revelation. If that requires Revelation to have been written before AD 70, so be it. (I'm not sure that it does require that; John could have been writing something as "prophecy" to explain events that had already taken place, as a kind of literary conceit.)
“An angel told Daniel to “seal up the book” because they described things which would happen 500 years after he wrote. An angel tells John that he’s writing about events which “must soon happen,” and they’re 2000+ years in the future? Doesn’t make sense” —> good point.
If Revelation has already happened then where is Christ? Christ returns at the end of revelation so where is he if revelation has already happened?