But the tools are trained on tons and tons of mediocre work and will have a strong tendency to output such. Please share your prompts aimed at preventing mediocre code entering the code bases you work on.

So far almost no code I got from LLMs was acceptable to stay as suggested. I found it useful in cases, when I myself didn't know what a typical (!) way is to do things with some framework, but even then often opted for another way, depending on my project's goals and design. Sometimes useful to get you unstuck, but oh boy I wouldn't let it code for me. Then I would have to review so much bad code, it would be very frustrating.