The truth is found in the Bible. No more things need be added to what has been written by the apostles and first century Christians who were inspired by God's holy spirit.
The apostles actually detected a spirit of rebellion and false teaching while they were alive and were inspired to write to warn us that there was going to be an apostasy after their death.
Any claim that there were things not in the Scriptures but were passed down by word of mouth and should be followed is part of that apostasy that was prophesied. The apostasy took complete control when the Roman government took over the church by decree at the council of Nicea in 325 C.E..
Some today refuse to look into the Scriptures for themselves. They believe the apostasy teachings because they are told to and it is convenient for them because they have been told that if they just follow blindly their soul will go to heaven the moment they die. They cling to a 1,700 year old tradition invented by the Roman council of Nicea instead of studying the Bible for themselves. The Roman emperor coerced a certain faction of so-called christian leaders to bend over and become the harlot of Revelation 17:1, 2. The apostles were very well aware that this would happen after they all died, for they actually saw it beginning before they died.
2 Thessalonians 2:3-7 says Let no one in any way deceive you, for it will not come unless the apostasy comes first, and the man of lawlessness is revealed, the son of destruction,
4who opposes and exalts himself above every so-called god or object of worship, so that he takes his seat in the temple of God, displaying himself as being God.
5Do you not remember that while I was still with you, I was telling you these things?
6And you know what restrains him now, so that in his time he will be revealed.
7For the mystery of lawlessness is already at work; only he who now restrains will do so until he is taken out of the way.
The pagan Romans wanted to continue observing their practices dedicated to disgusting false gods that Christ and his Father hate, so they accumulated for themselves the harlotrous religious leaders to fashion so called christian names and reasons to continue observing the practices disgusting to the true God.
2 Timothy 4:3 says For the time will come when they will not endure sound doctrine; but wanting to have their ears tickled, they will accumulate for themselves teachers in accordance to their own desires.
The apostle John was the last one to be in the way of "the man of lawlessness" (the Roman emperor and his successors) and knew that true worship was ending and the apostasy would quickly set in after his death.
1 John 2:18 says Children, it is the last hour; and just as you heard that antichrist is coming, even now many antichrists have appeared; from this we know that it is the last hour.
The trinity god was a Roman god that became one of the disgusting things renamed as christian at the council of Nicea.
The Jehovah's Witnesses are not the only ones who know these facts. Anyone who studies the history of religion and the Bible will quickly learn these facts. Then, if they want to truly serve God and not merely follow their religious leaders blindly, they will leave off and no longer believe the lie of the pagan trinity god. There is of course those who want an easy and convenient god that does not require them to do anything but merely says 'just say you believe and you will have life after death in heaven'
2 Thessalonians 2:11 says For this reason God sends them a powerful delusion so that they will believe the lie.
partially copied from another R&S dude