If you declare “mystery” out of order then you rule out a lot of religion by default, since many religions teach that the human mind can not grasp the divine or the infinite.
And if you say “I won’t accept mystery as an answer” then you have said nothing more than simply “I don’t believe in religion”. Which is fair enough, but it doesn’t amount to an argument that will convince anyone who does not already agree with you.
It seems to me the basic disagreement is over the two positions:
1. The true nature of reality is something the human mind cannot grasp.
2. The human mind is capable of grasping the true nature of reality.
I am not aware of any way of settling the issue in favour of one or the other. I tend to hope that 2 is generally true, but I also happen to think that it implies the existence of God. If God does not exist then it seems safer to assume that 1 is true. So we have a paradox at the heart of human knowledge.