Interestingly, most so-called 'pagan' religions were not in any way concerned with 'salvation'. The exclusionary principle seems to belong exclusively to the Abrahamic religions, and of the three, only Christianity and Islam are proselytising religions concerned with conversion and salvation,

The Greeks, Egyptians and Norse, for instance, based one's fate in the afterlife on one's deeds in life, not on which gods you served or worshipped. Certainly initiation into specific Mysteries might give privileges in the Greek afterlife, just as dying in battle was the passport into Valhalla for the Norse, but even these were not exclusionary. (My Odinist son tells me that the Welsh infantrymen and Zulu impis who fought against each other at Rorkes' Drift are now feasting together in Valhalla!)

Hinduism and Buddhism are also non-exclusionary, believing that everyone, at some point in their serial incarnations, will reach the goal.

I strongly suspect that Yeshua's beliefs and teaching were non-exclusionary, and that maybe the original cult based on them was the same. Somewhere, however, the concept that anyone could follow the way transmuted into the idea that everyone MUST follow the way.