I have react projects from less than 6-7 years ago that are bit-rotted because of changes to react. I have wanted to add features but can't because I don't have the time to fix everything that rotted.

To be clear, it's not 100% react. It's the entire ecosystem around it. Want to take wigdet-x v3 for bug fixes. It requires newer react, which may or may not be compatible with widget-z I'm using. Newer react requires newer tools which aren't compatible with the configuration that was created by create-react-app from 2 versions ago. etc...