I always considered myself agnostic leaning atheist. I consider leftism to be antithetical towards religion. All religions have a class structure to them, do priests, rabbis, or imams not exist? And what about marxism, is karl marx not venerated by some leftists in a weird atheist sort of way?
Read Durkheim on religion to understand that the fundamental building block of a religious system is social interaction and to therefore understand that religion under alienating capitalism is hollow because of it. Communism will have religious spirituality from the social interaction when groups become larger than the sum of their parts but the material realities will mean a priest class won’t need to form to distribute the limited resources.