Ok, but... how does that differ from Plato's position, let alone undermine it? My (admittedly limited) understanding is that Plato didn't believe that forms had instantiations "in the real world", either (except for things like squares, which I maintain do have real world instantiations). Plato thought the forms existed as metaphysical constructs, ones we presumably experienced on a spiritual level. The fact that many forms do not have real world instantiations is not, in and of itself, sufficient to refute Plato. In fact, it sounds to me like you're agreeing with Plato, except for...