I don't think the junior/senior distinction is useful in this case. All software engineers should care about the quality of the end product, regardless of experience. I've seen "senior" engineers doing the bare minimum, and "junior" engineers putting vastly more care into their work. Experience is something that is accrued over time, which gives you more insight into problems you might have seen before, but if there's no care about the product, then it's hardly relevant.
The issue with LLM tools is that they don't teach this. The focus is always on getting to the end result as quickly as possible, skipping any of the actually important parts of software development. The way problem solving is approached with LLMs is by feeding them back to the LLM, not by solving them yourself. This is another related issue: relying on an LLM doesn't give you software development experience. That is gained by actually solving problems yourself; understanding how the system works, finding the underlying root cause, fixing it in an elegant way that doesn't create regressions, writing robust tests to ensure it doesn't happen again, etc. This is the learning experience. LLMs can help with this, but they're often not used in this way.
The issue with LLM tools is that they don't teach this. The focus is always on getting to the end result as quickly as possible, skipping any of the actually important parts of software development. The way problem solving is approached with LLMs is by feeding them back to the LLM, not by solving them yourself. This is another related issue: relying on an LLM doesn't give you software development experience. That is gained by actually solving problems yourself; understanding how the system works, finding the underlying root cause, fixing it in an elegant way that doesn't create regressions, writing robust tests to ensure it doesn't happen again, etc. This is the learning experience. LLMs can help with this, but they're often not used in this way.