I have notice that until now that anytime Manchester United failure is mentioned people usually just bring Ten Hag into this discussion, man has been done his part and has left I think it is high time Manchester United fans and Ronaldo fans allow him to rest. Even the great Alex Ferguson made transfer mistakes, fell out with top players and the club moved on from it. One thing that baffles me with this Ten Hag banter and why I think it is coming from a point of hatred is he is never associated with players doing well but his name is quick to be mentioned with players not doing well. He signed wrong players and also did signed and promoted good players
Each person may have a different way to view a certain case. There are people who assume the mistake is something normal. It happens in every era of coach, even it was happening in Ferguson era as well. So, there is no need to talk about it so much. However, there are also the people who don't easily forget the mistakes, they will try to repeat talking about it many times. This type of people can be categorized as fanatic fans or haters. I personally also feel uncomfortable with these people. But I'm not trying to argue and waste my time with them, it is better to let them talking alone. 
By the way, Ten Hag already won few trophies with Man United although he failed to win EPL trophy. At least, he won FA Cup and English league Cup. These proved that he isn't a too bad coach.
Ten Hag's achievement: https://www.transfermarkt.com/erik-ten-hag/erfolge/trainer/3816