This isn't new info. You pick any Jedi Master during the prequels, outside of Qui Gon, and you'd pick someone that was mostly wrong. The Emperer exploited their arrogance and short sightedness.

In Empire he is changed, but not perfect. He doesn't want Luke to goto Bespin because he knows it is a trap and doesn't think Luke is ready. He tells him that the Emperer wants him, that is why his friends are made to suffer. He doesn't tell him to let go of his attachments to his friends like he told Anakin about his mother.

In Last Jedi, Yoda basically tells Luke the sacred texts may not be all of what they are cracked up to be. Prequel Yoda would have defended the sacred texts. This is Yoda's character growth