Urgh. I feel the stodge of relativism weighing down on me.
OK, yes, all models (and people) are wrong. I'll also allow that usefulness is not the same as verisimilitude (truthiness). But there is externality, even though nobody can as you say "perch" on it: it's important that there is objective reality to approach closer to, however uncertainly.
I'm willing to grant non-symbolic externality. Though, I don't know how useful that is.
We will never access the signified only the signifier. When we believe that signifiers exist externally, we are engaging in a suspension of epistemic honesty, and I get why we do it - it makes talking about and engaging with the world infinitely easier. But we shouldn't ever believe our own trick. That's reverting to a pre-operational version of cognition.
OK, yes, all models (and people) are wrong. I'll also allow that usefulness is not the same as verisimilitude (truthiness). But there is externality, even though nobody can as you say "perch" on it: it's important that there is objective reality to approach closer to, however uncertainly.