I'm fairly certain that Pope isn't talking about having sex in heaven. It's about whether the pleasure of orgasm can be considered a foretaste of the bliss of heaven.Contrary to what most Christians believe, there will be no physical bodies in heaven. The physical body once dead remains dead. It does not rise from the grave.
In heaven we will have spiritual bodies made up of heavenly elements that exist in the heavenly realm. Since they won't be physical, physical pleasure such as sex will not exist in the afterlife.... There will be only spiritual pleasure. Anyone who died attached to the physical pleasures such as sex will be in a hell of their own making because hell is wanting what you can no longer have and having to think about it for eternity. Moreover, anyone who died not even knowing what spiritual pleasures are will be utterly lost. That will also be hell.
We have one chance to acquire what we will need in the afterlife. That is why we were put on this earth, to acquire spiritual virtues. If we waste our lives living for the physical pleasures or other worldly desires we will be utterly lost after we die, but there won't be any way to go back and get what we have lost.
It is not a coincidence that all the Abrahamic scriptures teach the same things about the importance of the spiritual graces as opposed to physical pleasures and it is emphasized so much. It is not as if God has not given us fair warning. If we do not listen and do what is necessary we will pay the price. It is not God that will send us to hell, we will send ourselves to hell by being selfish and attached to this world. It might feel good now but it won't feel good after we die. Eternity is a long time to be in hell.
Christians (as well as Jews and Muslims) do await the resurrection of the dead and the Day of Judgement. So to them, we will be rejoined with our bodies eventually.