Many traditional prayers in Christianity mimic parts of the Bible which refer to "one God" as well as to "the only" son of God. This has been viewed, often by those who use such language, as a form of exclusivism.
That may be true, but is that all there is to it? What is being excluded?
One way of understanding "one God" is seeing it as a response to competition from or among gods. This is construed as an argument against the forms of polytheism prevalent in the cultures known from the periods in which the Bible was written. It is also a rejection of the claim that the notion of the Trinity is itself polytheistic. Yet it also contains an affirmation.
It affirms that whatever the name or image used, or with none at all, God is singular and unique. God is the ultimate concern of our lives underwriting all other concerns, even when one has no professed belief in a view of God produced by religion. God is the most real thing there is and is therefore sometimes described as ultimate reality. God is the source of existence and the deepest nature of all that exists.
This is a unifying statement. Believe this, doubt that, reject the other when it comes to claims about the divine. We are all connected to and through God. One world, one humanity, one God. Hence other religions and non-religions have an insight into God, however they conceive of and express it.
Something similar can be said for Jesus being "the only" son of God. The earliest known religions from the Middle East tended to claim their priest-kings were descended from the gods. The Roman Emperors of the era into which Jesus was born made a similar claim. The message of Jesus could easily be lost in the chorus.
Yet the imagery surrounding (and some would argue embellishing) the Gospels was geared to do two things: fulfill the expectations of certain groups of Jews that Jesus was the messiah and to challenge the conventional wisdom of the day. These were sometimes combined, such as the revelation that the proclaimed messiah wasn't going to conquer by force but by humility and sacrifice born of divine love, or that the Kingdom of God was not going to be a conventional political institution. Others included inverting the terms such as Gospel by having the great sage or king heralded by signs in the sky being born in poverty and relative obscurity.
Some "son of God".
More than this is the unique ontological status of Christ Jesus in the Christian understanding of God. Jesus talked about others being the children of God, so something else sets him apart. This is connected to the intentionality of God in becoming human as opposed to simply recognizing humanity as expressing and possessing an aspect of divinity. This act of explicitly linking what people would have perceived as the full dignity and holiness of God with human form is an act of solidarity with humanity.
This also has an affirming aspect. It has been argued that "the name 'Christ' [is] the 'Supername,' in line with St. Paul's 'name above every name' (Phil 2:9), because it is a name that can and must assume other names, like Rama or Krishna or Ishvara... Christ is the universal symbol of divine-human unity, the human face of God."
We need not simply accept merely the limiting interpretation given to such terms when their fullness is expressed in the context of unconditional and unequivocal love and acceptance.