Not the OP, but it might be that AI isn't as good at systems programming as it is at other domains, or it might be that you're using it differently than I am. I don't know which one it is (maybe AI just isn't good at writing the language you work with).
For things like web frontents/backends, though, it works beautifully. I ship things in days that would take me weeks to write by hand, and I'm very fast at writing things by hand. The AI also ships many fewer bugs than our average senior programmer, though maybe not fewer bugs than our staff programmers.
In my experience ai has had far far more bugs than most of what i call senior engineers but far fewer than juniors.
The boost is for what are glorified crud apps which it 1000x the tedious work. However, the choices it makes along the way quickly blows up without cleaning. Seniors know how to keep their workstation clean or they should.