LLMs can hurt less experienced engineers by keeping them from building an intuition for why things work a certain way, or why an alternative won't work (or conversely, why an unconventional approach might not only be possible, but very useful and valuable!).
I think problem solving is optimization in the face of constraints. Generally using LLMs IME, the more you're able to articulate and understand your constraints, and prescriptively guide the LLM towards something it's capable of doing, the more effective they are and the more maintainable their output is for you. So it really helps to know when to break the rules or to create/do something unconventional.
Another way to put it is that LLMs have commodified conventional software so learning when to break or challenge convention is going to be where most of the valuable work is going forward. And I think it's hard to actually do that unless you get into the weeds and battle/try things because you don't understand why they won't work. Sometimes they do