have been into Spiritualism for some bizarre reason
Most religions have afterlifes, and that implies some kind of spiritualism. And a mere 50+ years ago, Christianity was almost universally accepted in the West.
Of course, Sir Arthur Conan Doyle first rejected the Catholic faith of his Irish mother and father, and then passed through a phase of agnosticism.
Speaking of rejection, Agatha Christie was so deeply devoted to the Tridentine form of the Catholic Mass, that she signed a petition that resulted in Papal permission to extend celebrations of this Mass beyond the reforms of the Second Vatican Council. That permission became known as the Agatha Christie Indult.
But Christianity is irrational because it is based on Bible, and there are so many contradictions in the Bible. So whether Christianity rejects or approves Spiritualism doesn't tell us much.
Of course Christianity rejects ALL other forms of irrational belief. And so do all other "true" religions.
Buddhism is relatively cool however, it focuses on how we can alleviate suffering of living beings, not of spirits.
The church selected the relevant books, written by many authors over 1000 years. While some evangelical sects may claim internal consistency, it's mostly a straw man. The sources/purposes of the relevant books explain most inconsistencies already (namely that most Jewish law doesn't apply to gentiles, because Jesus was a new covenant with all peoples.)
Gospel harmonies deal with the biggest hole: The gospels don't have any reason to be inconsistent. But that's easy to respond to too: They were written in response to other writings, each other and popular ideas, in dialogue with each other, just as the "historical" books etc. or modern history books and internet comments are made in dialogue with each other. Christians say this approaches truth, where the order of events of Jesus' thorning are less relevant than his message of love etc.
This lens leads to many interesting readings, e.g. the bible can be seen as a vengeful god killing off other gods (by his chosen people killing worshipers of other gods) and then learning to be nice and instead choosing all peoples.
And, if you can't believe many parts of the Bible because they contradict each other, how could you believe that God has anything to do with the (creation of the) text of the Bible. Bible is clearly imperfect but we are supposed to believe that God is "perfect", because Bible says so.
Christianity is based on the conversation between God and His chosen people from the creation of the world until now, with that conversation moving towards and flowing from the Incarnation, Passion, Death, and Resurrection of the Second Person of the Trinity. Part of which is in the Bible (everything is not in the Bible alone - e. g. the list of the books of the Bible isn't in the Bible)
Mere Christianity by Lewis is a pretty good introduction to the idea, as is Orthodoxy by G. K. Chesterton.