Since when do claims of antiquity help one determine who is right?
If that is the case, the Jews of 2000 years ago had every right to point at the new followers of Jesus and tell them they were a bunch of upstarts.
When they extend back to a Founder who was Divine and rose from the dead to prove it.
(Sure beats a founder who was an occultist and Freemason from upstate New York, with a poor grasp of archaeology, a poorer grasp of theology, and an inability to keep his lecherous paws off the servant girls, doesn't it? Hey, you started this ...)
If that is the case, the Jews of 2000 years ago had every right to point at the new followers of Jesus and tell them they were a bunch of upstarts.
They did a lot worse than that. (St. Stephen the Protomartyr, pray for us.) Again, the only excuse for changing a Divinely-received covenant is when you receive a new Divinely-ordained covenant.
(Gold plates that nobody can produce, written in a language that nobody has ever heard of, relating events that never took place, do not qualify.)