The first (and maybe even second) usage of a gnarly, badly thought out pattern might work fine. But you're only a couple steps away from if statement soup. And in the world where your agent's life is built around "getting the tests to pass", you can quickly find it doing _very_ gnarly things to "fix" issues.
I think you're likely in the silent majority. LLMs do some stupid things, but when they work it's amazing and it far outweighs the negatives IMHO, and they're getting better by leaps and bounds.
I respect some of the complaints against them (plagiarism, censorship, gatekeeping, truth/bias, data center arms race, crawler behavior, etc.), but I think LLMs are a leap forward for mankind (hopefully). A Young Lady's Illustrated Primer for everyone. An entirely new computing interface.
Much like giving a codebase to a newbie developer, whatever patterns exist will proliferate and the lack of good patterns means that patterns will just be made up in an ad-hoc and messy way.