Cultural confinement takes place when a curator imposes his own limits on an art exhibition, rather than asking an artist to set his limits.

This quote means that when a curator decides which artworks to include in an exhibition, they might choose to be quite restrictive and limit which pieces are shown. Instead of allowing the artist to decide which pieces go in the exhibition, the curator decides which pieces fit within their own expectations and limits. This is called cultural confinement because the curator’s own views and beliefs influence the artwork that is ultimately shown.