Given the number of CC users I know who spend significant time on creating/iterating designs and specs before moving to the coding phase, I can tell you, your assumption is wrong. Check how different people actually use it before projecting your views.
I would argue that rapidly iterating reveals more about the problem, even for the most thoughtful of us. It's not like you check your own reasoning at the door when you just dive head first into something.
So even if it comes at the expense of long term maintainability - everyone should have this in their toolbox.
Having access to my local repository and my whole home folder is much easier than dealing with Claude or ChatGPT on the web. (Lots of manual markdown shuffling, passing in zipfiles of repositories, etc).
i think it still pulls to do then think because you cant tell what the agent understood of what you asked it to do from that first think, until its actually produced something.
Claude Code and similar agents help me execute experiments, prototypes and full designs based on ideas that I have been refining in my head for years, but never had the time or resources to implement.
They also help get me past design paralysis driven by overthinking.
Perhaps the difference between acceleration and slop is the experience to know what to keep, what to throw away, and what to keep refining.