Given that Buddhism could accommodate people's prior religious beliefs, why is Buddhism itself now described as a religion?

Read somewhere that Buddhism does not advocate to go away from the beliefs of a person. Or in a way accommodate one's rooted beliefs from childhood. The main objective of following the path of Buddha is for self-realization. That too not disturbing others and their beliefs. - Since Buddha advocated for education to all humankind without considering race or color, will it be like a revolutionary thought came before centuries (_like communism, socialism ..._)? - But most of the world refers to it as a religion. Is it because of the transformation to idol based community from a spiritual community created by Buddha? - Does Buddism has more affinity towards a free-thinking society based on modern science OR towards a ritual-based society based on fears that remind the mind to do good acts?