We're in the very early stages of LLM driven programming, so it's hard to say how it will all shake out, but my anecdotal experience is that LLM written software is very reliable and easy to extend and develop. I have a side project that is about 90% LLM generated code (about 25k lines of production code and a similar amount of test code). This is a revenue generating product and I've had no issues with reliability, security, or performance.
For what it's worth this app is a rails app and I have no plans to switch to anything else. Rails works nicely, the LLMs extend it easily, and almost everything is I/O bound so I don't need C++/Rust level performance.