Prior to Paul appointing himself as an Apostle and breaking ways with the Jewish followers of Jesus in Jerusalem
Right off the bat we got a problem. Scripture says that the other apostles accepted Paul as an apostle, they "added nothing" to his teachings, and they "gave him the right had of fellowship".
Then fourteen years after I went up again to Jerusalem with Barnabas, and took Titus with me also.
2 And I went up by revelation, and communicated unto them that gospel which I preach among the Gentiles, ...
7 But contrariwise, when they saw that the gospel of the uncircumcision was committed unto me, as the gospel of the circumcision was unto Peter;
8 (For he that wrought effectually in Peter to the apostleship of the circumcision, the same was mighty in me toward the Gentiles:)
9 And when James, Cephas, and John, who seemed to be pillars, perceived the grace that was given unto me, they gave to me and Barnabas the right hands of fellowship; that we should go unto the heathen, and they unto the circumcision.
Scripture says they were all preaching the same message and were in agreement. Peter, James and John, the big three gave him their blessing and "added nothing to my message" - Gal. 2: 6 NIV
Jehovah's Witnesses are obsessed with the earliest form worship that the followers of Jesus had. They were basically practicing Jews who also accepted Jesus' teachings. They still celebrated the Jewish festivals and went to the temple. That is why they were hated by the Sadducees, and Pharisees. It was their job to keep Judaism pure and free from non-Judaic religious belief or practice. Jehovah's Witnesses are an offshoot of that early, brief period that existed shortly after Jesus death.
I tend to agree with this. I would probably state it a little differently. JW's are obsessed with living in the prior dispensation (age of law) and the future dispensation (Millennium age) and do not live in the age we are now in... the age of grace.