LOS ANGELES — Modernism may be dead, yet we spend an awful lot of time in its clutches: talking about it, building it, watching it, exhibiting it, and acquiring its graceful artifacts for our homes. Our culture is in such a thrall to some of the movement’s architectural and artistic manifestations — Barcelona chairs! Case Study houses! paintings by Piet Mondrian! — that it can be hard to imagine a time when the very idea of its stripped-down forms inspired either passionate shock or jaded exhaustion.