If the tool is reliable, it's a win. Saved brain power doesn't disappear, it can be applied elsewhere.
If the tool is powerful enough to do a better job than our brains would, it's a big win. In fact, we built the entire technological civilization on one such fundamental tool: writing.
Or from another perspective: our brains excel at adapting to the environment we find ourselves in. The tools we build, the technology we create, are parts our environment.
This argument has held up in the past but there’s no certainty that during this current period where LLM’s are not perfect (and in many cases far from perfect) - they can ever become perfect that it’s fine for one’s existing human capital to depreciate.
If the tool is powerful enough to do a better job than our brains would, it's a big win. In fact, we built the entire technological civilization on one such fundamental tool: writing.
Or from another perspective: our brains excel at adapting to the environment we find ourselves in. The tools we build, the technology we create, are parts our environment.