No codebase worth being deeply invested in is deeply understood by anyone, including the original authors. The eternal maintenance argument is tiresome. If there is a problem in need of fixing, you figure it out, you do not depend on some author being available, and LLMs are exceptionally helpful in this regard as well. Then, if the LLM has trouble figuring out, so will another human. It is a code smell.

There are all kinds of projects out there that have had significant impact on the world, which were written and maintained over the course of years by a single, highly capable developer. The way people talk about code nowadays, just because they have more powerful authoring tools, is frankly disgraceful. Imagine if modern construction techniques had become a reason to stop caring about the natural beauty of wood grain.