The Nietzsche Stone is a modest object in a grand landscape: a boulder by Lake Silvaplana associated with Friedrich Nietzsche's summers in Sils Maria and the thought-world that fed Thus Spoke Zarathustra. It is the kind of place that matters only if you bring the story with you.
That story is enough for many travelers in the Engadine. The walk along the lake gives the stone its force, with mountains, water, and light doing more than any plaque could. Combine it with Sils Maria and the Nietzsche House rather than treating it as a standalone St Moritz sight.