Culture is not a container. We treat it as such when we speak of the culture(s) in which we live, or of moving about within a culture. We treat it as such when we talk about culture as a holistic system, of which we are all parts.
Culture as container suggests a (more or less) totalizing, (more or less) homogeneous, and (more or less) unchanging system. This view does disservice to the many subjects who are said to live within them. In spite of varying levels of independence and agency ascribed to subjects, culture as container ultimately limits their ability to affect and alter the system. They may be granted the ability to move about freely within the system, but they are not allowed to create something new.
In place of the container model, we can look at culture as a set of relations between many different kinds of entities. Not something we live within, but many things (material and semiotic, human and non-human) that we live amongst. In this sense, culture can be seen as a heterogeneous assemblage of assemblages - a heterogeneous, and historically contingent set of relations of sets of relations. Rituals, politics, modes of thought and behavior - these are heterogeneous assemblages which we as subjects (also heterogeneous assemblages) find ourselves amongst. We live with them, interact with them in complex ways, and they affect and alter us just as we affect and alter them.
If we are to make a difference with anthropology, then we need a concept of culture that leaves open that possibility: a complex concept of culture that does not reduce our agency to the mere ability to move, and that does not reduce culture to a container.