LLMs are a godsend when it comes to developing things that fit into one of the tens of thousands (or however many) of templates they have memorized. For instance, a lot of modern B2B software development involves updating CRUD interfaces and APIs to data. If you already have 50 or so CRUD functions in an existing layered architecture implemented, asking an LLM to implement the 51st, given a spec, is a _huge_ time-saver. Of course, you still need to use your human brain to verify before hand that there aren't special edge cases that need to be considered. Sometimes, you can explain the edge cases to the LLM and it will do a perfect job of figuring them out (assuming you do a good job of explaining it, and it's not too complicated). And if there aren't any real edge cases to worry about, then the LLM can one-shot a perfect PR (assuming you did the work to give it the context).

Of course, there are many many other kinds of development - when developing novel low-level systems for complicated requirements, you're going to get much poorer results from an LLM, because the project won't as neatly fit in to one of the "templates" that it has memorized, and the LLM's reasoning capabilities are not yet sophisticated enough to handle arbitrary novelty.