So it is clear that Ten Hag's selfish attitude was the main trigger for his failure to bring Manchester United back to its glory days. Therefore, Ten Hag really has to change his attitude if he really wants to be able to bring Manchester United to become champions. And you are right my friend, that this season will definitely be a defining season for Ten Hag. Because if Ten Hag fails this season, he will definitely be fired from Manchester United's coaching.
I removed some part of your post due to how lengthy it is. I don't think Manchester united management is ready to fire Ten Hang because there is no perfect time to fire him than at the end of last season when clubs who were not satisfied with their couch fire them. Everyone expected to wake up to the news of Ten Hang sack but were all shocked hearing that he will continue as the head couch. He has a very good relationship with the management crew and that's what is keeping him. I quite agree that they have players who have potential but then injury is giving them tough time and Ten Hang on the other hand doesn't know how to make good use of the available ones with his preference and selection.
The injured players was the excuse that Ten Hag used to prove that it was not his fault for the club poor performance last season and he was able to use just one match to convince united management on what he said by winning FA Cup finals which made Manchester united to consider him worthy of giving another chance.
Injuries have started again and Ten Hag should look for a way in which he will be able to manage the players on ground in order to maintain some level of performance and not just losing woefully Luke last season, so that if these injured player are fit again, it can be easy for the team to catch up with other clubs on top four and also finish on top four next season.