I am quite sure you are making the same mistake that most non believers make. You are thinking of changes that Christian people have made in the way they view scripture or doctrine and confusing that with the faith it's self. The Christian religion is not to be thought of as whatever a person claiming to be a Christian does or thinks. It is based on the original revelations of God given almost 2000 years ago and that has never and will never change. If you walk by a car and say it is red, then I walk by and say orange does that mean the car changed colors. It means me and you see different but almost identicle things but the car is the same. I don't give a rip what any particular Christian claims, it is God's revelation that does not change. The modern bible is 95% the same as the original. The other 5% is mostly grammer not meaning. However it does have a few percent of meaningful differences. 2% meaningful inaccuracy is certainly not grounds by which to claim that the religion has changed especially since the modern bibles point out and footnote even this 2%. Even if the bible had significant errors compared with the original that still wouldn't mean that God has changed or the actual religion.
The Spirit of Christ is a living thing. And like all living things it must adapt to changes.
I have no evidence that Jesus Christ ever wrote anything down.
Many years later several writers tried to capture His essence in words. Around 325A.D. a group of powerful men met and decided which of these writing would be canonized.
This was the first power move by the privileged.
They then began to impose laws based on their interputation of Gods will.
The results led to things like the "Inquisition". No one was excluded. Though they put on a face of obedience, they had to know in their hearts that all this had it's roots in evil because the Spirit of Christ teaches forgiveness, tolerance, and understanding.
Some Christians seem to be content to sit and read their scriptures and pass judgement on the rest of the world based on a document of the times that was written 2000 years ago.
The Prince of Darkness seems to be content with this. Many Christians are lukewarm and no threat. There are to many things going on to be worried about what can disrurp the evil that surrounds us.
The Spirit lives on and it is more powerful than ever.
It is so easy to tap into this power in faith and truth.