Even if LLMs write more buggy code they can still bring up software quality in the short to medium term by allowing you to clear out a lot of the backlog of bugs and UI issues that are known but never had enough priority to be fixed

Debugging and developing first fixes is also one of the spaces where current LLMs are the biggest force multipliers. Especially if you have reproduction cases the LLM can test on its own

But long-term it might look very different as more and more of the code becomes LLM written