What if God were just but not merciful? Would He still be good? No. [Scott David Allen, Why Social Justice is not Biblical Justice (Gradn Rapids, MI: Credo House Publishers, 2020), 28]
What shall we say then? wIs there injustice on God’s part? By no means! For he says to Moses, “I will have mercy on whom I have mercy, and I will have compassion on whom I have compassion.” So then it depends not on human will or exertion, but on God, who has mercy. (Rom. 9:14-6)
The relation between God, justice and mercy is a touchy topic, in that it affects each of us personally. Most people read Scripture in a way that favors their particular concepts of justice and mercy, in a way favorable to them. Yet, God is not mocked. We can ignore what He Himself has said, but His Word remains there, immutable and true.
Would God be just even if He was not merciful? For mercy to be mercy, it must be undeserved and not obligatory. An "obligatory mercy" implies that God owes it to the creation or creature to show mercy. Even if it is said that God owes himself, that makes "mercy" something that the creature can demand of God, just that the ground of demand is shifted to the being of God. But nobody can demand mercy of God, so therefore it can never be obligatory of God.
If mercy is not obligatory, then by definition it cannot be said that God must be merciful. Therefore, the goodness of God exist independently of whether God has mercy. That is the point of Romans 9:14-16. It is ultimately God's choice whom He will have mercy. God does not have to have mercy on anyone in order to be good, contrary to the assertion of Scott David Allen. In fact, God can choose to not have mercy on anyone and yet He would still be good and just. That is why sinners saved by grace owe gratitude to God, because God does not have to save us at all.
The grace of God is the basis of God's mercy. It is the grounding of Christian mercy, which likewise is not owed to anyone. That is why it is called "mercy" and not "entitlement." By definition, something that is of "mercy ministries" cannot be demanded. By definition, when something that cannot be demanded is withdrawn, that is not cruelty, because the recipient is not entitled to it. It does not matter how needy the person is; he still is not entitled to mercy.
That is precisely the problem here with many "mercy ministries" today, because they fail to understand what "mercy" is. Just because someone is in need does not imply that anyone, neither society nor any individual save for their family members, is entitled to any help whatsoever. The problem with many "mercy ministries" is that they should rename themselves to "entitlement ministries," because that is how they think as they go about working for "social justice." They are of course free to spend their money however they want, but they are not entitled to call themselves "mercy ministries" and so falsely advertize themselves.