Actually nobody is preventing you from building library with LLM.

On top of it you can in parallel work on the library, groom its shape and then have another workflow integrating that library into bigger library and so on.

The biggest issue I always had was integration between components. Today's that's free lunch. You can extract, abstractize, re-integrate things for free.

Long before LLMs there was a concept of Big Ball of Mud. The slop existed before LLMS and all software eventually rotten. Today just as LLMs whip out faster the code rot happens faster too.

But engineers learned way into how not to make systems decay fast and (not surprisingly) the same methods work just as well with LLMs.

I find LLMs like a blender. If you are ignorant in use everything will become a tasteless grey sludge. But it's a indispensable tool in a kitchen that makes many things simple, easy and tasty.