‘Outside are the dogs, and the occult-seekers, and the sexually misbehavers, and the murderers, and the idolaters and every one who makes and loves a lie.'
Compare Revelation 21:8; Revelation 21:27. Throughout the book these things have been illustrated and condemned. Dogs in those days were mainly disreputable and disease ridden creatures as they scavenged around cities, and cities always sought to exclude them. Here we are told that men reveal themselves to be ‘dogs' when they engage in the occult, in sexual misbehaviour, in murder, in putting loyalties before God and in lies and deceit, especially in believing the great Liar, and they too are then excluded. The warning is clear. Make sure you are in.
This cannot seriously be taken to demand that those mentioned are waiting there, standing outside. They are outside because there was no welcome for them. The point is that they are ‘outside' because they have been excluded. They are the opposite of being in. They are, in fact, at this time in the lake of fire (Revelation 20:15).