The comparison has force only if "mystery" means the same thing in both cases. Islam allows that Allah's reality exceeds our grasp, but it does not ask us to affirm a contradiction or divide divinity into persons.
The strongest form of the criticism
The critic says: Muslims reject the Trinity because it is beyond reason, yet they accept doctrines that also seem beyond reason. They say Allah has real attributes, but these attributes are "neither identical to Him nor other than Him." They say the Quran is Allah's uncreated speech, yet hadith describe the Quran as coming, interceding, and arguing on the Day of Judgment. If the attributes are not Allah, they look like created additions. If Allah needs them, He is not self-sufficient. So, the charge is: Muslims are using "bila kayfa" - without asking how - to excuse their own mystery while condemning Christian mystery.
What "without asking how" is actually doing
"Without asking how" is not a license to believe nonsense. It is a boundary between two things: knowing the meaning of what Allah revealed, and claiming to know the mode of Allah's reality.
There is nothing like unto Him, and He is the Hearing, the Seeing.
Quran 42:11
This verse holds both sides together. Allah truly hears and sees; these are not empty words. Yet His hearing and seeing are not like created hearing and seeing. The meaning is affirmed; the creaturely "how" is denied.
So when theologians say the attributes are not simply identical to the essence and not other than Him, they are guarding two truths. They are not identical in meaning: knowledge is not power, and speech is not will. But they are not "other" in the sense of separate beings, parts, partners, or additions attached to Allah. Allah was never without knowledge, power, life, will, or speech. His attributes are eternal, not contingent things that came to be.
The uncreated Quran and the hadith of intercession
The doctrine of the uncreated Quran means that Allah's speech is not a created product outside Him. Allah speaks as befits Him. The ink in a mushaf, the paper, the sound of a reciter, and our memorization are created. What they convey - Allah's speech - is not created.
The Prophet (PBUH) said:
Recite the Quran, for it will come on the Day of Resurrection as an intercessor for its companions.
Sahih Muslim
And he (PBUH) described al-Baqarah and Aal Imran as coming and arguing on behalf of those who recited them. Scholars did not understand this to mean that Allah's eternal attribute becomes an independent creature that debates Allah. Rather, Allah may create a form, reward, or representation connected to the recitation, or He may make the Quran's recitation a cause of intercession. The hadith teaches the honor and benefit of living with the Quran, not that there is a second divine entity beside Allah.
Why this is not the same as the Trinity
Muslims do not reject the Trinity merely because it is hard to imagine. We reject it because it conflicts with the oneness Allah revealed and because its claims are not the same kind of mystery. To say "Allah has knowledge unlike created knowledge" is not like saying "there are three distinct persons, each fully God, yet not three gods." The first affirms one necessary Lord with real perfections. The second introduces personal distinctions within divinity that, from the Islamic view, compromise pure monotheism.
And there is none comparable to Him.
Quran 112:4
So the objection establishes a useful caution: Muslims should not mock every doctrine simply for being beyond full human comprehension. But it does not establish a double standard. Islam distinguishes between mystery without likeness and contradiction without warrant. Allah is known through what He revealed, while His reality remains greater than the mind can encompass.