I'm arguing that there's a skill that has to be learned in order to break through this. As you start in a new code base, you should be quick to jump in when you hit that 20%. But, as you spend more time in it, you learn how to avoid the same "context hell" issues and move that number down to 15%, 10%, 5% of the time.
You're still going to need to jump in, but when you can learn to get the LLM to write 95% of the code for you, that's incredibly powerful.