In the case of unhelpful human support, I can leverage my experience in communicating with another human to tell if I'm being understood or not. An LLM is much more trial-and-error: I can't model the theory-of-mind behind it's answers to tell if I'm just communicating poorly or whatever else may be being lost in translation, there is no mind at play.
That's fair, though with an LLM (at least one you're familiar with) you can shape it's behavior. Which is not too different compared to some black box script that i can't control or reason through with a human support. Granted the LLM will have the same stupid black box script, so in both cases it's weaponized stupidity against the consumer.