You haven't considered that I probably already discussed 10 different approaches with my agent before authorizing a particular implementation. Or that I didn't ask about alternatives during review. You're confusing physically coding with thinking. You can still think just fine without writing code yourself.
If you are experienced, attentive, curious, willing to explore, etc., that doesn't change after an LLM allows you to deeply discuss any concept at will, quickly try different prototypes and zone in on the correct implementation. You will use these tools to their full extent.
> Why exactly a piece of code is the way that it is cannot be determined by just reading the code.
If you maintained a good commit history and your code is self-documenting and you're not capable of understanding and navigating code you read, you can still literally just ask the LLM to explain the code within the context of the codebase. They are extremely good at that exact task. They will give you as much as you give them. If you want to know, and can understand, the nitty gritty, you can do that and no one is stopping you.
> Reading a mathematical proof does not give you any meaningful understanding of it.
Again: these things can function as personal tutors. Run the proof through an LLM and ask it what you care about. Furthermore, there are plenty of elegant proofs you can read which confer "meaningful" understanding.
Before just assuming that everyone telling you these tools are useful is less capable or experienced than you, it's worth considering if it's actually you who needs to maintain an open mind and attempt to learn from others.