I see nothing merciful about babies with genetic disorders, diseases, malnutrition, etc. So far I've shown more concern for the kids of the world than any god and I am only human.
The life of the World is not the goal; the next spiritual life is the purpose: where man will live for millions of years.
All creatures are limited and restricted:
Man and all other created beings are limited and restricted in everything: if he lifts 40kg, he cannot lift 50kg; and if he runs at a certain speed, he cannot run faster. Similarly are all his thinking and other capabilities.
God restricted all His creatures, or else His created being will be like god. The creature whatever it be is limited and restricted; but God is Infinite and His might is unlimited and unrestricted.
The suffering in the life of the World:
So man in the life of the World suffers much of everything from his birth till his death; and he needs His Creator God Almighty and Most Gracious.
The needs of man are many and everyday man has other needs: if he desires to have a son, next day he will desire to have another son or daughter; if he desires for a house and God gives him what he required of Him, he next year will desire to have a wider house with a wider garden …etc.
So man in this life of the World is always suffering, then comes God's mercy and grace to moderate his suffering and ease his way.
The purpose is the afterlife:
The purpose or the aim is the next spiritual life not this material life in this World.
This World is only a school: a primary school where man learns skills and acquires experience until he is about 40 years when his mind will mature and his wisdom is about complete.
At the same time this Woldly life is only an examination and checking and trial to attain his grade in the next afterlife.
How man acquires his knowledge and experience:
That is through suffering and experiencing the happiness and the misery, the health and the disease, the richness and poverty …etc. So if he does not feel ill sometimes, he will not know what the blessing of the health is, and if he does not suffer the economic need, he will not know what the richness grace …etc.
The affliction of man in this World:
Moreover, whatever hard circumstances face man, it will be better for him (if he is devoted to God alone and forbears patiently and do not blaspheme), while he is usually unaware of that.
E.g. the young child is very dear to man, but when God tries him with the death of his son, it will be very difficult like a stabbing in the heart; to this many men blaspheme and revile God Most Gracious;
while if he forbears patiently he will go to Paradise and find his son still a young child alive there and he will be delighted with him; and none in Paradise has any child of his own excepting the one whose child died in the Word; because the soul does not grow but will remain as it is: if he dies a child, his spiritual soul in Paradise will be a child.
The afflictions are because of the sins and disobedience:
In addition, the sins of people will bring on them the punishment: if they steal the property of each other and wrong each other and the weak will complain to God, God then will punish that community and that wrong-doing man or community.
Such punishment includes many incurable diseases like the cancers and AIDS…etc.
The reason why God is Merciful to Christians and disbelievers in this World:
And when people are merciful to each other, then God will be Merciful to them; like Christians: many of them are merciful to each other and cooperate with each other and their mercy extended to involve the animals
à so God has been Merciful to them in this World only and has given them their recompense [of their good work] in this World only, but in the afterlife they will lose because many of them denied the Quran and Prophet Mohammed: His apostle and the religion of the Islam and devotion to God alone.
[This is drived from the Quran interpretation by Mohammed-Ali Hassan Al-Hilly, the late interpreter of the Quran and the Bible.]
Those who know Arabic see the interpretation of the ayat 4: 29, 30