I also agree with you, The main backbone of a team is a responsible coach of that team. A coach is the most important behind the success of a team. A team can maintain a good consistency on the playing field due to the good practice of a responsible coach. And currently everyone dislikes the coach of Manchester United team, because currently no player of Manchester United team is performing well in Erik ten Hag's practice. They are losing most of the games, even against some weak teams, they are not able to survive. Manchester United team needs another responsible coach to replace Erik ten Hag at the moment, but Manchester United will be back again in great form.
Be responsible with your job is good but not enough. You must be capable of doing a good job too and to achieve it, responsibility is not enough. You need other things like capability in tactics and management so that you can draw a long term good strategy of team development while in short- and medium-term, you will still be able to ensure acceptable results for the team.
I don't call Ten Hag is irresponsible head coach but to say him as a great coach, I don't think so.
Yes, it seems that this season is again difficult for Manchester United to break into the top three, in my opinion they will also find it difficult to break into the top four or reach the Champions League zone. Erik Ten Hag clearly has not made any impact since he entered Old Trafford, even though if you look at the amount of investment, the Red Devils are already able to compete at the top of the standings.
Erik Ten Hag has been given enough time with more than two seasons and enough budget to buy many players to improve their squad in his favorite plans but he has failed seriously with his plan. This season can be a last chance for him to rescue his job in Manchester United but it seems early matches are more likely strong warnings that he is counting down very last matches in the club.