Manchester United didn't do well in the beginning of the season last year and they are doing the same this season. In the last two games they lost unexpectedly vs Crystal Palace in EPL and Galatasaray in Champions League. Defensive errors are unforgivable in such highly intense competitions and injuries couldn't be an excuse there.
Their next two games aren't that hard before returning again in Champions League and facing just next Manchester City. I am not very optimistic about them in Champions League nor vs City.
I understand, for the most part I agree with you, but I stated in my post the fact at the end of the season that things have more or less normalised. Injuries to players are something that the coach can't influence, so it's hard for me to say that in this case injuries don't play a role, they just directly influence it
Player injuries have certainly affected the team's performance, especially if it is the main player. There are many cases where a team loses its best form when one or two of their key players are absent due to injury, remember Liverpool last season?
However, it's not just player injuries that have hit Manchester United, the performance of their key players has dropped significantly compared to last season. Rashford is the player who is increasingly being talked about, but there are several others too. So it's no surprise why Manchester United's performance this season seems poor, there's clearly a reason instead of just blaming Ten Hag.
So I think the absence of one or even two key players on the pitch has a coordinated effect on the result, maybe that's why MU players have become worse. Ten Hag's problem that can be blamed on him is that he can't find a competent replacement for an injured player, but that's the most I could charge him with..