Sometime between 1982 and 1984, I borrowed a book from the school library, which was about a powerful alien civilisation visiting Earth. Humanity asked for medicines and technology to help with its problems. Instead, the aliens ask for their help and take a group to a primitive planet to solve a problem. The humans realise that their technology would affect the planet badly - the aliens then explain that's why they can't help humanity.
I have the impression that the book may have been written sometime before the eighties.