The word doctrine means what is taught.
The word theology comes from the word theory.
In regard to the Bible specifically and within the various religious systems ... there are many theories of what it is actually saying ... based on a accepted theory(s) that is what is taught (doctrine) and they vary. Agree on some points and not on others. So people debate the differences.
Each of us are responsible to search the scriptures for ourselves. We are to do this to prove or disprove what is being taught (doctrine). However, many do not do this and just accept whatever doctrines (teachings) are being brought forth from whatever church they go to. Many do not even take their bibles with them to church.
Do not misunderstand what I am saying the Bible is not theory ... it is the true living word of God. However the understanding of it varies.
Jeremiah 29
13 You will seek me and find me, when you seek me with all your heart.
Recognize that the Bible is its own interpreter and that the meaning of words, texts, and passages is best determined by diligently comparing scripture with scripture. Search for overwhelming "evidence" .... scriptural evidence.
Always pray for the Holy Spirit to guide you in the truth.
God Bless