However, from my experience, the quality of code produced by developers in project we are working for the last 3+ years gone south. Amount of bugs now literally tripled year on year. I bet the reason is extensive use of AI tools, as the developers are the same.

Its because most people don't have the discipline and obsession of attention to detail to know when one should use an LLM and when one shouldn't.

I highly doubt the best of the best folks are even touching LLMs (barely) because they can see the flaws and the tradeoffs that are not-so-visible to others until they are 50 levels deep, with sunk investments, unwilling to go back to how they used to do things.