To answer your specific question:

Around LLM usage:

• harness engineering (god I hate this word salad)
• workflows : define requirements to production monitoring going through QA

Around general knowledge:

• low level language is important. C or Rust to me are your best options unless you want to go game dev, then C++ would be your choice
• Design system and scaling. Time and space complexity
• Testing is a huge differenciator to me. A junior that really got "testing" is way ahead of others

Now my 2 cents about your actual words. Your first sentence is worrying to me. LLM writes code for you. But the app is you. You are saying it writes the app for you, this brings some questions: what is your value? What did you learn? For what purpose? Was your main problem writing code?

Writing line of code is like 0.01% of our job. It feels like it's important, but we are talking about "typing letters in a text document". 90% of the work is knowing what to type. Sure the LLM seems to know what to type, but it's actually not. You've been giving rails to the LLM so it goes a specific direction, but if you aren't able to assess the final position you are in, are you confident in the code it produces?

Ownership of the code is a big part of our job. Understanding it, being able to anticipate and answer questions about it. What happens when the devs still needs ownership of the code but delegates to the LLM the writing of the solution? The devs needs to review every line of code very carefully. This ends up in reading code of someone else. And this is harder than writing the code yourself. So... What's the gain? Where's the value? You work harder to not do the easy thing, feels weird no?

Your brain is the value. LLM writing your code isn't a good idea, especially if you're learning. Use your LLM to help you do the job, not do your job, else you're just useless. Anyone can ask a LLM to create an app.