Does the Scriptures teach that a Christian is to be "rightly dividing the word of truth" ?(2 Tim 2:15, King James Bible) No. God's word of truth is not to be ' divided ', such as the churches of Christendom have divided the Bible into an "Old Testament" and "New Testament".
Rather an accurate rendering of 2 Timothy 2:15 is that a Christian is one that does "your utmost to present yourself approved of God, a workman with nothing to be ashamed of, handling the word of the truth aright", in which there is no Old nor New Testament, only one complete book called the Bible.(New World Translation)
The apostle Paul used the Greek word orthotomounta (a compound word formed from two Greek words, orthos [G3717] and tomos [G5114]) that means "(1) to cut straight, (2) to handle aright, i.e. to teach the truth correctly and directly".(Thayer's Greek-English Lexicon of the New Testament, pg 453)
Hence, a true Christian must be able to distinguish between what is truth of the Bible, and what has been presented as "truth" by the churches of Christendom, but under careful examination is false. Jesus gave an illustration at Matthew 13:24-30, in which he explains the illustration at verses 36-43, whereby he shows that "wheat" or true Christians would distribute Bible truth, but they were oversown by "weeds" or imitation Christians, sowing falsehoods about God and his eternal purpose for mankind.
For example, Jesus stated in the illustration that he as "Son of man" sowed "fine seed" in his "field" or the world of mankind.(Matt 13:24, from 29 C.E-33 C.E.) But not long after establishing the Christian congregation ("congregation", from Hebrew qahal meaning "call out, congregate" and Greek ecclesia [also formed from two Greek words of ek meaning "out" and kaleo meaning "call"] meaning to "call out" or be ' called out ' by God from the world under Satan's rulership into his "congregation" of loyal ones that came into existence on Pentecost 33 C.E.), apostate elements were being "sown" by "weeds" or counterfeit Christians among the "wheat" or true Christians, so that after the death of the last of the apostles (John in about 100 C.E.), or "while men (the apostles who were a restraint to the rising tide of apostasy, 2 Thess 2:6, 7) were sleeping, his enemy (the Devil, Matt 13:39) increased his business of oversowing "weeds" with their falsehoods.
The "wheat" was almost completely swallowed up by the "weeds" from the second century on until the "harvest" or our time period, that began in 1914 with Jesus installation as king of God's Kingdom, when "the Son of man will send his angels, and they will collect out from his Kingdom all things that cause stumbling and people who practice lawlessness".(Matt 13:41) At that time, the "wheat" or true Christians began to be separated in earnest from the "weeds" or counterfeit Christians that make up Christendom and were organized into the "congregation of God".(Acts 20:28)
So, what religious falsehoods have the "weeds" sown ? (1) the Trinity (John 14:1, 28; 1 Cor 11:3), (2) hellfire (Jer 7:31; 19:5; 32:35), (3) immortality of the soul (Gen 2:7; Deut 12:20; Jer 2:34), (4) clergy-laity class (Matt 23:8-10), (5) purgatory (Ecc 9:5, 10), (6) observance of religious holidays such as Christmas (Luke 22:19, 20), Easter (1 Cor 11:23-26), Halloween (1 Cor 10:21), birthdays (Gen 40:20-22; Ecc 7:1; Matt 14:6-10), feast days for "saints"(Acts 10:25, 26), (7) that participation in the political arena has God's blessing (John 15:19), (8) that there is no need to go from "house to house" with the "good news of the Kingdom", teaching "deserving ones" through a home Bible study (Matt 10:7, 11-13; 24:14; 28:19, 20; Acts 20:20), (9) that pagan traditions have more scriptural force than God's word (Matt 15:3-9), (10) that God's name of Jehovah should be supplanted with "Lord" or "God"(Ex3:14, 15; Ps 83:18; Jer 23:27), to name a few.
Thus, Christendom's Christianity is a blend of pagan teachings and practices with just a "smidgen" of truth.