"But when you have to scale the work, then the code has to be easy to read, easy to extend, easy to test, have extensive test coverage, have proper dependency injection / be easy to mock the 3rd party dependencies, be easy to configure so it can be deployed in every cloud provider (i.e. by using env vars and config files for modifying its behavior).."

Interestingly I do not find that the stuff you mentioned are the things that LLLMs are bad at. It can generate easy to read code. It can document its code extensively. It can write tests. It can use dependency injection especially if you ask it to. What I noticed where I am currently am much better than an LLM is that I can still have a very nuanced very complicated problem space in my head and create a solution based on that. The LLM currently cannot solve a problem which is so nuanced and complicated that even I cannot fully describe and work partially from insincts. It is the 'engineering taste' or 'engineering instincts' and our ability to absorb complicated nuanced design problems in our head that separates experienced developers from LLMs.

Unless LLMs get significantly better and just replace humans in every task, I predict that LLMs effect on industry will be that much less developers will be needed but those who will be needed will be relatively 'well paid' as it will be harder to become a professional software developer. (more experience and engineering talent will be needed to work professionally).