In an academic paper I am trying to argue that there is a stark difference between neoliberal capitalism and traditional religions (Islam, Christianity, Buddhism etc.). Do you know of any philosopher who has tackled this question?
Would your topic change if you omitted 'capitalism' and referred simply to 'neo-liberalism' instead ? Perhaps it would - I only pose a question.
Approach via logic
One approach might be to consider if one could adopt Buddhism, Christianity or Islam and consistently support neo-liberal capitalism. E.g., is 'I am a Christian and I support neo-liberal capitalism' a contradiction ? Formally at this level of abstraction there is no contradiction but can Christianity and neo-liberal capitalism be further specified to the point where one could say whether they are mutually independent or contradictory? You could pursue this line of inquiry.
Approach via ontology
The following is one viewpoint:
... religion provides symbols, rituals, and an ethic that, taken together, give deeply satisfying answers to core ontological questions about the coherence of the universe, the purpose of human life, the nature of evil, and the reasons for suffering and death. Smith argues that Christianity provides a set of answers to these ontological questions that is deeply satisfying on an emotional level, and that is why it has been so successful across the span of history. (Penny Edgell, 'We Still Don't Know If Christianity "Works," Much Less Why: Response to Smith', Sociology of Religion, Vol. 69, No. 4 (Winter, 2008), pp. 445-452: 445; C. Smith, "Why Christianity Works: An Emotions-Focused Phenomenological Account." Sociology of Religion 68:165-78.)
For your purposes the angle here might be that neo-liberal capitalism is unconcerned with such questions and deflects attention from them. A culture that valorises neo-liberal capitalism does not interlock with one that gives central importance to the kind of ontological questions indicated. So there is not a logical contradiction but a social-psychological mismatch.
Better suggestions may well be made in other answers. Here I simply open the topic with two possible approaches. My own views don't make an appearance.