Christ may have the authority on Earth, but He doesn't seem to have actually put it into effect at this time.
The President of the United States is obviously Joe Biden. Is Joe Biden's authority in effect right now? Of course it is, right? And, yet, there are plenty of people who oppose him. But that opposition doesn't take his authority away. Similarly, Christ's authority is in effect now regardless of whether everyone obeys Him or not.
See Revelation 11:15, which tells of the future:
"Then the seventh angel sounded; and there were loud voices in heaven, saying, “The kingdom of the world has become the kingdom of our Lord and of His Christ; and He will reign forever and ever.”
And then 2 verses later:
"saying, “We give You thanks, Lord God, the Almighty, the One who is and who was, because You have taken Your great power and have begun to reign."
Clearly, these things haven't happened yet. So in the meantime, the kingdom of the world isn't the kingdom of God, and He has not begun to reign.
That is talking about God the Father reigning when the Son delivers His kingdom to the Father, which He will do when He returns.
Do you agree that Jesus will return at the end of the age (Matthew 24:3)?
This is what Jesus said will happen at the end of the age:
Matthew 13:40 “As the weeds are pulled up and burned in the fire, so it will be
at the end of the age. 41
The Son of Man will send out his angels, and they will weed out of his kingdom everything that causes sin and all who do evil. 42 They will throw them into the blazing furnace, where there will be weeping and gnashing of teeth. 43
Then the righteous will shine like the sun in the kingdom of their Father. Whoever has ears, let them hear.
Do you see here that at the end of the age the kingdom is called "the kingdom of their Father"? That is because Jesus will have delivered the kingdom to the Father at that point, as Paul taught here:
1 Corinthians 15:22 For as in Adam all die, so
in Christ all will be made alive. 23 But each in turn: Christ, the firstfruits; then,
when he comes, those who belong to him. 24 Then the end will come, when he hands over the kingdom to God the Father after he has destroyed all dominion, authority and power. 25 For
he must reign until he has put all his enemies under his feet. 26
The last enemy to be destroyed is death.
What Paul taught in the passage above is that all of the dead who belong to Christ will be resurrected when He comes again. It is at that time that the end will come and He hands over the kingdom to God the Father. Paul said that Jesus must reign until He has put all His enemies under His feet. That means He is reigning now and will continue to reign until He returns to take vengeance on all of His enemies (2 Thess 1:7-9).
Notice that it says the last enemy to be destroyed (or defeated) is death. If you continue reading further in 1 Corinthians 15, you can see when that will occur.
1 Corinthians 15:51 Listen, I tell you a mystery: We will not all sleep, but
we will all be changed— 52 in a flash, in the twinkling of an eye, at the last trumpet. For the trumpet will sound, the dead will be raised imperishable, and we will be changed. 53 For the perishable must clothe itself with the imperishable, and the mortal with immortality. 54
When the perishable has been clothed with the imperishable, and the mortal with immortality, then the saying that is written will come true: “Death has been swallowed up in victory. 55 “Where, O death, is your victory? Where, O death, is your sting?”
It is when Christ returns at the last trumpet that death will be defeated and "swallowed up in victory".
It's interesting that you referenced Revelation 11:15-17 but said nothing about verse 18.
Revelation 11:18 The nations were angry, and
your wrath has come. The time has come for judging the dead, and for rewarding your servants the prophets and your people who revere your name, both great and small—and for destroying those who destroy the earth.”
The seventh trumpet marks the time "for judging the dead". Is the judgment of the dead not described in Revelation 20:11-15? Sure, it is. So, that places the timing of the seventh trumpet as occurring after the thousand years. It also marks the time for rewarding His people and "destroying those who destroy the earth".
Jesus said He is coming "to give every man according as his work shall be". That lines up with what it says will happen at the seventh trumpet because it signals the dead being judged and His people being rewarded.
Revelation 22:12 And,
behold, I come quickly; and my reward is with me, to give every man according as his work shall be.
Being judged according to what people have done? That's exactly what is described in Matthew 25:31-46, which occurs when Jesus returns, and what we see described here:
Revelation 20:12 And I saw the dead, small and great, stand before God; and the books were opened: and another book was opened, which is the book of life: and
the dead were judged out of those things which were written in the books, according to their works. 13 And the sea gave up the dead which were in it; and death and hell delivered up the dead which were in them: and
they were judged every man according to their works.