For a human to be able to do any customization, they have to dive into the code and work with it, understand it, gain intuition for it. Engage with the maintainers and community. In the process, there's a good chance that they'll be encouraged to contribute improvements upstream even if they have their own fork.

Vibe coders don't have to do any of this. They don't have to understand anything, they can just have their LLMs do some modifications that are completely opaque to the vibe coder.

Perhaps the long term steady state will be a goldilocks renaissance of open source where lots of new ideas and contributors spring up, made capable with AI assistance. But so far what I've seen is the opposite. These people just feed existing work into their LLMs, produce derivative works and never bother to engage with the original authors or community.