Imagine you're learning soccer. One friend keeps saying: “You're the best! Your kicks are amazing!” but really you still miss a lot. The other friend says: “You're improving! But you need to practice dribbling more.” Which one actually helps you grow?
Flattery is when we say what the other person wants to hear, not what they need. It looks like kindness, but it's a trap for both people: you don't improve, and your friend loses your trust when the truth comes out. Jesus never flattered anyone. He told the truth, with love, but without hiding it. And that's why the people who met Him were transformed.