LLMs benefit juniors, they do not replace them. Juniors can learn from LLMs just fine and will actually be more productive with them.
When I was a junior my “LLM” was StackOverflow and the senior guy next to me (who no doubt was tired of my antics), but I would’ve loved to have an actual LLM - it would’ve handled all my stupid questions just fine and freed up senior time for the more architectural questions or those where I wasn’t convinced by the LLM response. Also, at least in my case, I learnt a lot more from reading existing production code than writing it - LLMs don’t change anything there.