Don't know why people are so against De Boer. In his short time here he made some tactical mistakes for sure but I felt like we got an early glimpse into his gameplan working at full potential (when we completely outplayed, and last beat juve) and then didn't see enough of that again. Part of that is on him for sure but I personally felt he deserved more time.
His post-Inter career has been laughably horrendous but I think that's partly a mismatch of him and the clubs he's working at. To greatly simplify things, I feel like de Boer has some decent technical skills and tactical knowledge, but not the means to back it up. He's probably too "highbrow" for the clubs he's recently managed, not to mention too stubborn for his own good. For example, I feel like if he took over at Barca tomorrow and all the players magically just respected him and did exactly as he instructed without question, he'd do pretty well. But as we all know, Crystal Palace is not Barcelona, and players do not magically respect you unless you prove yourself. And those seem to be his failures - enforcing a complex style of play on teams completely unequipped to play that way, without 'proving himself' and losing both on the pitch and in the locker room as a result.
I felt he was pretty likeable tbh. Whether people want to put his remarks regarding Inter down to bitterness is up to them but I didn't feel like anything he said was wrong. Put it this way, if Mourinho said about Man U, the same things de Boer said about Inter, most people would agree with him. Because Mourinho has 'proven himself'. Shame really. I feel like de Boer could be a good coach if he had a squad technically capable of executing how he wanted to play. But the world doesn't work like that. Even if you have the skills to be a great CEO, no company just gives you control of the company without you having proven yourself. You gotta work up from management etc. I'm not saying he's an elite coach by any means, but if de Boer is even a quarter of the coach I think he can be, he really needs to moderate his methods to better suit smaller teams for him to achieve some success and rebuild his reputation.