It's the end of open-contributions for one specific repository, that is all. It only covers QGIS, the UI application, not GDAL/GEOS and the other libraries that give it its functionality. Additionally, in the past few years the number and popularity of new open-source projects that do accept open contributions far exceeds the few old ones that do not.

GDAL isn't too big on LLM contributions either.

You're forgetting QGIS's own plugin ecosystem, which afaik doesn't prohibit slo-... err, vibe and assisted-coded contributions.

Although that would probably change of the AI-assisted spam shifted over to it.