I disagree. They were way more than a plot device. They *were* a plot device, but they were also, broadly speaking, Asimov's reaction to the visceral anti-robotics fears of the early days of sci-fi, a way of speaking out against the idea that AI would invariably go crazy and start murdering people for the luls, or because they wanted us out so they could take over, or whatever other reasons. He very intentionally wrote stories in which robots were not just intelligent, but intelligently *designed*, with rules explicitly created by humans to prevent the sort of chaos one saw whenever robots showed up in the media he was responding to.
Then, yes, they *were* a plot device, as he spent the next forever finding all the different ways the simple laws could go wrong, but there *was* a broader message.
That said, I do find it irritating when people who are *not* living in the Asimov robot fictional universe, seem to imagine they're "laws" in the scientific sense, as opposed to, obviously, laws in the "obey the law" sense. Asimov's fictional robots were designed with those laws baked in, but we can design robots however we like. (Heck, on a few occasions, people found ways of messing with the laws at the root level in his fiction, too, if I recall.)
And yes, in this case, it's all totally irrelevant, as there's no intelligence. There isn't even any goal-seeking, which *would* be more amusing and at least more likely to cause discussion, if it just wandered around randomly looking for humans and jabbing them (though the result of the discussion would be "wow that guy is a dick for making a machine that did that.")