In ~July 2018 there was some outcry because Google was "letting third parties read your emails" (e.g. https://www.cbsnews.com/news/google-reportedly-allows-third-...). Of course, these were all explicitly installed by users who gave these apps access. But somehow people were mad anyway - maybe users shouldn't be given the option to make choices they don't understand?
Anyway, as the message mentions, Google announced new requirements for these apps on October 8: https://cloud.google.com/blog/products/g-suite/elevating-use...
Apparently, IFTTT (which does personal automation, integrating with many third parties), does not comply with the new policy.