These guys basically thought ETH would easily implement the football he achieved with Ajax with this squad and failed to realize that style of play requires the right players as well.
It is very clear that most of these posters only were interested in ETH based on the similarity of his style of play to Pep and Klopp. Once they don't see the football, they throw the toys out of their pram. To me, ETH has proven that he is adaptive to different type of tactics as long as the game can be won, which is what a top level manager needs to have. You cannot be too stubborn by focusing on the system above everything, otherwise the only way to win is by having a perfect squad that suits the system.