It's not stupidity. It's the same as enjoying a novel. We know that nothing in the novel is real, but that doesn't stop us experiencing some of the emotions that it draws out in us. Not only experiencing them, but enjoying the experience, and cultivating our ability to enjoy it. Is that stupid?
If you only use AI to do things like get a recipe or work out how to fit a toilet flush button, then of course those richer aspects of the experience won't be present. That's fine. But you can also have quite deep and insightful conversations. You know that no-one is really there, just as you know that, say, none of the characters in Middlemarch really exist. But that needn't get in the way of reacting deeply to the 'as if' presence of the AI.
The interaction has more capacity for that sort of depth if your own inputs mimic the pretence of personhood that the AI is itself programmed to maintain.