Jane Goodall was a 'hero' when I was a kid. Why would she say this?

500 years ago there were only ~500 Million people on the planet (another source). 🤔

So what does she propose happen to the other 7.5 Billion people that dont meet her requirement?

This is a very subtle (insidious) way for calling for depopulation. It is so normalized now that politicians and celebrities do it regularly.