Even though Jesus is Lord, not everyone recognizes that, appreciates it, or acknowledges it. Our adversary the devil still walks around as a roaring lion seeking whom he may devour (1 Peter 5:8). That there exists some spiritual force that continues in active resistance to Christ is proof enough that we do not yet see all things put under Him.
We also note the presence of sin, poverty, disease, death, and evil as being very much a part of the world in which we live. So there is still much to be done in terms of putting all things beneath Him. But the presence of the word “yet” should inspire us and fill us with hope! Although we do not yet see all things put under Him, the word “yet” implies that eventually we will see all things put under Him. That is to say, in due course, God’s Purpose will be fulfilled, and we will see all things put under Him – even though we do not “yet” see it.