It's all about the quality of your prompts (i.e. your skill at writing clear unambiguous instructions with correct terminologies).

An experienced developer can generate tons of great code 30x faster with an Agent, with each function/module still being written using the least amount of code possible.

But you're right, the measure of good code isn't 'N', it's '1/N' (inverse), where N is number of lines of code to do something. The best code is [almost] always that with the least amount of lines, as long as you haven't sacrificed readability in order to remove lines, which I see a lot of juniors do. Rule of thumb is: "Least amount of easily understood LOC". If someone can't look at your code for the first time, and tell what it's doing, that's normally an indication it's not good code. Claude [almost] never breaks any of these rules.