I can talk about mysteries quite a bit, actually.
From an evangelical point of view we have solid scripture. “The mystery of godliness is great.” Now here’s an interesting detail in what follows: “Vindicated by the Spirit.”
Oh, that is so, so much more than the events of the literal bible era. Christ is vindicated by the Spirit NOW.
The acid test of a mystery is... what does it serve to vindicate, or seem to vindicate? Is glory going to God? Or to some ungodly entity? I see problems in the Roman Catholic system, but to be charitable some of them came because the church WAS open to mystery. Doing mystery means being able to get the mystery wrong or distorted. I also see problems with evangelical critiques because they discount the Conquering nature of Christ. For example, a Christmas tree is a CHRISTmas tree because of Christ. It’s been snatched out of any satanic clutches it might have attracted in the past.
And God said He is like a fir tree, it's biblical why we put up a tree at the time of the conception.