Its a sad, but inevitable, fact that almost all of Christian theology - is merely defensive parroting.
Which is to say that the discourse is just people expounding arguments and evidences they have learned from sources approved by the church to which they have chosen to affiliate.
It is awareness of this parroting quality (on one or both sides) that may produce that sense of frustration at lack of engagement, of unseriousness, of insincerity - or even cowardice; which has been so off-putting to so many modern people who are considering becoming Christians, or who are expressing genuine (not merely expedient) doubts about aspects of their church or Christianity generally.
I suppose there must have been some people who were actively thinking about Jesus Christ and Christianity at some point in history! Indeed, I suppose that the letters of Paul are evidence of this kind of grappling.
But there has been in Christianity, and very early, and for most (not all) of subsequent history - probably as in most other religions - a strong tendency to draw a line under this thinking for oneself - and a switch to stating (dogmatically) that this primary engagement has been done, the results are in - and the answers are as follows...
From which point the idea is that good Christians need to understand and believe, to learn and rehearse, and to parrot.
At which point there is no point in talking to them! Arguments are futile! Debate is simulated!
Unless - that is - you are merely curious about such people; or if your goal is to become like them, and be guided in all your fundamental life understandings, motivations and choices - by an institution. Which is, evidently, still a popular aspiration - although almost-never actually achieved.
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Further Note: I have often myself engaged in this defensive parroting! So I know it by inner experience.
For instance, in medicine, doctors explanations are of this kind, because the doctor has never himself been through the background to medical facts and claims, but is merely repeating what he has been taught or otherwise learned.
And, of course, most enquiries and dissenting directed at doctors is (almost inevitably) itself shallow and ignorant, or selfish or manipulative... and is not motivated by a genuine desire for discovering truth.
But Not Always! And then it is maddening to have one's one direct enjoyment met with parroting merely!
At other times, after becoming a Christian, I sometimes found myself in the same situation. I accepted the truth of some external claim - but did not really know it for myself or from primary experience - and indeed such experience tended to refute the external claim, but I deferred to authority on the basis that cleverer and better informed people than myself had been deemed to have sorted-this-out long ago.
It was really when I - almost against my will - was nigh-compelled to dig deeper and deeper towards the most fundamental aspects of Christianity; that I began to find it ever more obvious that this would Not be how God would set-things-up!
I mean; I began to feel clear and sure that God would Not create us and the world; such that we were supposed to pick some particular social institution (a church), then adopt an attitude of obedient service and trusting credulity to that institution.
That would be an absurdly unreliable, fragile, contingent way to plan a system for the salvation of Mankind!
At around this point, I began to notice when I was parroting about Christianity, and to dislike myself for doing it; and instead felt a necessity to discover the truths by my own thinking and spiritual experience.
And to regard such personal engagement as the bottom line for my understanding of reality - rather than regarding Christian faith as deference-to and parroting-of any particular external source.