It occurs to me, before someone has pointed it out, that if salvation is made evident through the life of different individuals, some (or many) of whom are not even related to Christ-centered beliefs, why is there any need for particularism or Christ-centeredness. It is a good question, and one I have thought about. I have chose the narrative answer.
I can only make sense of those actions that potentially reveal salvific meaning if I have an actualized event that I can relate them to.
The story of Jesus, part of the larger story of YHWH and Israel, or Creation and Creator relationship, lends context to the events that I hear about, observe, or participate in. Jesus is the language of my experience, and the provides the baseline for my understanding of actions or events that pose revelatory value.
Of course, I can become a student of Gandhi, or a student of Buddha, and I can incorporate specific claims made by the followers of Hinduism or Buddhism into my framework of knowledge. Ultimately, however, my immersion in the Christ-centered faith of my original spiritual experiences will act as a filter, and I will generally not do justice to those claims.
If I do fully immerse myself into Hinduism or Buddhism, and become a "professional" so to speak, then I have either began to view the world through a worldview different than that of my original Christ-centered faith, or I have come to further identify with it and have no need for the assistance of other views that may act to distort the Christ-centeredness of my particular narrative.
Of course, I can combine the best aspects of Hinduism, Buddhism, and Christianity (It seems no one ever chooses Islam) and live accordingly, but then this would be a new religion, necessarily rejected by the proponents of each of the original faiths. This is not to suggest that their is anything wrong with new religions (or old ones). It is only to suggest that spiritual or religious intelligibility and integrity must not only allow for the particularity of all religious claims, but must allow them to maintain their particularity and identity over and against mutations that insist upon co-opting the old identity by painting the new religion as the natural evolutionary advance of the old.
Remember, evolution is not (necessarily) an unquestionable improvement. It is an adaptation to an environment. Early followers of Jesus were certainly not out to improve on Palestinian Judaism, and I don't believe they were an adaptation of it. It was a continuation of the Yahwist faith by making a specific claim that was only intelligible within the Yahwism of its time. Messianic claims did not in anyway change the nature of the way God was acting or to act in history, according to Judeans of the first centry. they fully expected God to act, most simply rejected that Jesus was the person the YHWH acted through.
Whatever has happened to the Christ-centered witness over two thousand years, it is the witness that God's desire is fully revealed in the historical Christ, and that those who believe that the life Jesus lived is normative for our understanding of humanity that lends context to our understanding of the world around us. If I understand the world through Jesus, with an assist on the goal from Buddha, then I may be a better person for it, but I am no longer Christ-centered.
there are, of course, several implications for Quakerism in my thinking, but I don't have to spell those out. Blessings to all.