It may be worth considering how much the impact of LLMs is exacerbated by friction in the contribution process.

Many projects require a great deal of bureaucracy, hoop-jumping, and sheer dogged persistence to get changes merged. It shouldn't be surprising if some are electing it easier to just vibe-customize their own private forks as they see fit, both skipping that whole mess and allowing for modifications that would've never been approved of in mainline anyway.