However, it gaslights like a pathological liar
This is a weird outcome and contrary to the experiences of most users. The tendency that is commonly observed is that, on the contrary, agents don't really "hold opinions" and flip-flop the moment you start challenging them. I'd be curious to learn what model and setup gave you an agent that defends its hallucinations because that is definitely an outlier in a world of sycophantic models that have been RLHF'd to hell and back.
and does the things it’s been specifically told to not do, and does so repeatedly.
In my experience, this is a tell that you are holding it very wrong. You can shit on models for having no creativity or losing track of long horizon tasks but following instructions is the one thing they do well. Again, stupid model or stupid harness, or you're just not holding the pointy end in the right direction.
The tech is advertized as a replacement for human programmers
US tech marketing is done by assholes targeting morons. It is probably safer to never, ever take their statements at face value.
There are 2 categories of people who are dead wrong about agentic coding : rabid vibe-coders who think it 10x their productivity (it doesn't, it just exacerbates their worst tendencies), and people like you who think it's good for nothing. Both categories are just vibing based on a gut feeling. But in the middle there is a whole spectrum of actually interesting experimentation, if you are ready to fist fight your personal assumptions and be fact-based about it.