Its actually a mercy because if it was clear as you want it to be then , we would have to belief or face the fire. Without a second chance. This way you still have time to consider and change your mind.
The greats signs of God/Allah are his Prophets (upon them all peace). They all came forward with miracles in order to prove their claims; you can see this with every Prophet who performed miracles with Gods/Allah permission.
In fact Muslims believe that when mankind was created then God/Allah raised up all of mankind and asked, "Am i not your Lord?" They all said, "Yes, We testify." This is a proof against us all.
So its up to you. For me at least I want to be in heaven and I believe in God/Allah. I don't want to be like those who reject God because they rejected paradise. There is an afterlife and it begins when we die.