Humans make mistakes too, does it mean humans are unusable? We accept as empirical fast that most production quality code has 2 - 10 bugs per 1k LoC. According to your premise, virtually all existing software is therefor unusable.
What if an LLM overall starts to make less mistakes than a medium developer, costs less than its salary and is 100 x faster? For sure, the companies that will leverage these with just a few senior devs doing prompting, testing and requirements analysis, will outcompete other organizations.
Humans make mistake then to learn from it. A really good expert would never deliberately copy-paste an obscure solution from the internet, then to ask for forgiveness later.
AI agents do that, perhaps not always, but still do. Now the question: would I trust AI without verifying its output?