We all admit that Ten Hag's first season was fantastic compared to the first seasons of coaches like Klopp or even Pep. There is no club that can suddenly be on fire and consistent, especially with a new coach, everything needs a process, for example, Man City, which has been superior in the last few seasons in the EPL since being acquired by Sheikh Mansur, has very strong financial strength but was only able to win the UCL last season.
I don't want to judge Erik Tag as a failure at this point, because there are still 30 matches left in the EPL and the journey is still very long. Regarding Ronaldo and De Gea, I think every coach must have their own set of goals for the team. We know Ronaldo is no longer young and Erik Tag needs young players, as does De Gea, he is a good goalkeeper but does not suit Erik Tag's strategy which cannot build attacks from the goalkeeper.
Though Manchester United are underperforming this season but I don't think it from Eric Ten Hag even though he's got a little side of the blame based on his decision making and late hour substitutions that cause them to lose matches sometimes but he's a good coach and he proved that last season by winning a trophy for united and finishing in the top 4, the problem with Manchester united is injury crisis and lack of investment on the wrong players, I believe if they had invested on the right choice of players they would've done better than this, though some players they got are performing well though.
Well there's no coach that hasn't experienced failure and i believe ETH is at one of the worst phase of his career and it's left for him to work hard for his team to get better, every coach has their decision to make whether it affects the team positively or negatively and his decision to let Ronaldo leave wasn't all bad cause they still finished top 3 and won a trophy but allowing Degea leave Manchester United and replacing him with Onana is a wrong decision.