The way I see it it is sort of like debugging code you're not well accustomed with.

While you're still going to learn whether you go through the hassle of understanding the system, develop a method for debugging it and learning about it along the way...

Of course a senior could point you to the issue right away, probably an llm too, and even provide a learning opportunity, but does it hold the same lasting impact of being able to overcome the burden yourself?

Which one makes a more lasting effect on your abilities and skills?

Again, LLMs are a tool, but if people in school/college start using it to offload the reasoning part they are not developing it themselves.