We can try another one.
People in a room on fire in a burning building. We'll forget for a moment that you created the people and the fire, and make you just a fireman.
They're running willy-nilly, total confusion, some even further into the fire. You have a special machine that can instantly transport them all harmlessly from the fire.
You have the power to save all the people in the room. Only you can choose whom to pull from the fire and you can easily choose them all.
You don't. Just a few. The rest you just watch as they burn alive.
Now, what would you say about the kindness and compassion of the fireman?
Not the same.
First, your analogy looks at sin as mere confusion - not the evil act of will that it is.
Second, God is not a fireman. A fireman is obligated to fight fires. You can not obligate God to do anything. He is God. He will be consistent with His justice and holiness and will show mercy as He wills and will give grace as He wills, but He is not obligated to give His creatures any more than He has already given them. In fact, He isn't obligated to do anything for them. He is the potter. They are the clay. If He wishes to destroy all in the fire, He can do so. The fact that He doesn't is pure mercy.
But even at that, even if a fireman were a good analogy of GOd, you havent' given the correct view of the fireman. You see, the fireman not only cleared a path for escape accessible to all, but put His very life on the line and offered to stand in the fire for them if they would just leave. All they had to do was enter the path that He prepared. Yet, they refused. In fact, they hated the fireman. They loved the fire. They would rather burn than turn towards the fireman. They spit upon the very gift He gave them and ignore His path instead deciding to pursue their own path.
True, the Fireman has the power to save everyone in the room yet the more He reaches towards the people the further they run.
He is just in allowing all to burn. But in order for others to see the consequences (Which they never could without His allowing some of the consequences to play out); He chooses to save some of them while allowing the others to follow their desired course.