First, it isn't a few seconds. It's a few seconds + the time it takes you to review the code to make sure it is correct. Second, in my experience I write the code no slower than the time it takes an LLM + the time to review it. Sometimes I'm faster, and my code is certainly better. The only thing where LLMs actually provide a boost is snippets which are so trivial that I can review them almost instantly, and which I can read but would be laborious to write (like bash scripts).